Objects – teachanyclass.org

Introduction

In 1945, a mathematician sat down and designed a machine that had never been built before. He called it the Automatic Computing Engine, or ACE. It was intended to be a general-purpose computer: a machine that could be given different sets of instructions and do different kinds of calculation. The mathematician's name was Alan Turing. He had spent the war years at Bletchley Park, the British code-breaking centre, where he led the work that broke the German Enigma code. Historians believe that breaking Enigma shortened World War Two by perhaps two years and saved millions of lives. After the war, Turing joined the National Physical Laboratory in London to build his computer. He designed the ACE in remarkable detail. But the project moved slowly. The full ACE was never built. A smaller version, the Pilot ACE, was built after Turing left — it first ran on 10 May 1950. When it ran, it was the fastest computer in the world. It is now in the Science Museum in London, the oldest complete general-purpose computer in existence. At the same time that Turing was designing the computer that would shape the modern world, the British state was treating him as a criminal. In 1952, Turing was arrested and prosecuted for having a relationship with another man. Homosexuality was a criminal offence in Britain at the time. Turing was convicted. He was given a choice: prison or chemical castration — hormone treatment that was meant to suppress his sexuality. He chose the hormone treatment. In 1954, Turing died. He was 41. A half-eaten apple was found beside him. The official verdict was suicide, though some have questioned this. In 2009, the British Prime Minister issued a formal apology for the treatment of Turing. In 2013, Turing received a royal pardon. In 2021, his face appeared on the British fifty-pound note. The machine he designed is in a museum. His name is on a law that has posthumously pardoned thousands of gay men prosecuted under the same laws. His test for artificial intelligence is still used today. The lesson is about what one man built, and what was done to him.

The object

Origin: Built at the National Physical Laboratory, Teddington, London, England. Based on the design of Alan Turing, who left the NPL before it was completed. First run on 10 May 1950.
Period: Designed by Alan Turing in 1945-1947. Built 1949-1950. Operated at the NPL until the mid-1950s. Now a permanent exhibit at the Science Museum in London.
Made of: Vacuum tubes (thermionic valves) for logic and calculation — fewer than 1,000 in total, compared to about 18,000 in the American ENIAC. Mercury delay lines for memory: 12 tubes each 1.5 metres long, each storing 32 instructions. Metal chassis, wiring, and Bakelite components.
Size: Roughly 2.4 metres wide, 1.5 metres tall, and 0.6 metres deep. Occupied a large room when in operation, along with its power supply and cooling equipment. Clock speed: 1 megahertz — which made it for a time the fastest computer in the world.
Number of objects: There is one Pilot ACE. It is the only surviving example and is considered one of the most historically significant computers in existence. It is the oldest complete general-purpose stored-program electronic computer surviving anywhere in the world.
Where it is now: Science Museum, London, England. On permanent public display.

Before you teach this — reflect

Questions for you

Turing's prosecution and treatment were the direct result of laws targeting gay men. How will you teach this honestly, including the specific nature of what was done to him, without making it either overly clinical or sensational?
Turing is now celebrated as a national hero in Britain. How will you help students see the difference between posthumous celebration and genuine justice?
The lesson involves both extraordinary scientific achievement and serious historical injustice. How will you hold both together, without letting one diminish the other?

Common student difficulties — tick any you have noticed

My students may not know the basic facts of Alan Turing's life: mathematician, World War Two code-breaker at Bletchley Park, designer of early computers, prosecuted in 1952 for homosexuality, died in 1954 aged 41.
My students may not know what the Enigma code was or why breaking it mattered. They may have seen films about it, which may or may not be accurate.
My students may not know what a stored-program computer is or why Turing's design was different from earlier calculating machines.
My students may not know that homosexuality was a criminal offence in Britain until 1967, or that thousands of men were prosecuted under these laws, or that many have since received posthumous pardons under what is informally called 'Turing's Law'.
My students may not know that chemical castration was the specific sentence Turing accepted as an alternative to prison.
My students may not know that Turing's fifty-pound note, his royal pardon, and the public apology all came after his death. They are forms of posthumous recognition, not restoration of what was taken from him.

Discovery sequence

1

In 1936, a 24-year-old Cambridge student published a paper that most of the world did not understand. Alan Turing was thinking about a question in pure mathematics: what are the limits of what can be calculated? His answer was to imagine a theoretical machine — now called a Turing machine — that could follow any set of rules given to it. If a mathematical problem could be expressed as a set of rules, the machine could in principle solve it. This idea was not a practical computer. It was a thought experiment. But it contained the fundamental idea that would become computing: a machine that can be reprogrammed to do different things by giving it different instructions. This is what makes your phone the same kind of object as a hospital computer or a weather forecasting system. They are all universal machines running different instructions. Turing published his paper before most people had heard of electronics. He was imagining machines made of pure logic. Why might a thought experiment from 1936 still matter today?

Points to consider (for the teacher)

Because it described the thing before the thing existed. Most inventions work the other way: someone builds something and then works out what it can do. Turing worked out what a computer could do before any computer existed. This kind of ahead-of-time thinking is very rare. Turing's theoretical model defined the outer limits of what any computer can calculate — this is still true of the most powerful computers today. Every computer you have ever used is, in a formal mathematical sense, a Turing machine. Students should see that mathematics is not just calculation. It is also the discipline that asks: what are the limits of what is possible? Turing asked this question about computing and answered it correctly, before computing existed. This is one of the most powerful intellectual achievements of the twentieth century.

2

When World War Two began, Germany used an encoding machine called Enigma to send secret military messages. The machine scrambled messages using a system that changed every day. German commanders believed the code was unbreakable. Alan Turing was recruited to work at Bletchley Park, a secret facility in the English countryside. There, a team of mathematicians, linguists, chess players, and crossword enthusiasts worked to break German codes. Turing led the mathematical work on Enigma. He designed a machine called the Bombe, which could test millions of possible Enigma settings quickly and find the day's key. Breaking Enigma allowed British and Allied forces to read German military communications. They knew where submarines were going. They knew where attacks were planned. They could change their responses. Historians differ on the exact impact, but many believe breaking Enigma shortened the war by at least two years and may have saved millions of lives. After the war, Turing's work at Bletchley Park was classified under the Official Secrets Act. He could not tell anyone what he had done. The full story was not made public until the 1970s. What does it mean to do essential work that nobody knows about?

Points to consider (for the teacher)

For Turing, it meant that his contributions to the war effort were invisible. When he joined the National Physical Laboratory in 1945, he was a brilliant but relatively unknown academic. The government officials he worked with did not fully understand his wartime contribution. This affected how seriously his ideas were taken and how quickly his computer project moved. There is a broader point here about the relationship between secrecy and recognition. Turing did things that saved enormous numbers of lives. He was never decorated. He was not publicly celebrated during his lifetime. The people who knew what he had done could not say so. Students should think about the difference between doing important things and being recognised for them. The two do not always go together. Many people do essential work that history does not record. Turing is one of the more dramatic cases where the gap between contribution and recognition was enormous — and where the state that benefited from his work later persecuted him.

3

The Pilot ACE ran its first program on 10 May 1950. At the time, it was the fastest computer in the world, with a clock speed of 1 megahertz. It could handle calculations that would have taken human computers weeks, in minutes. Turing was not there. He had left the National Physical Laboratory in 1948, frustrated by the slow progress of the project. He moved to Manchester University, where he worked on the Manchester computers and continued his theoretical work on artificial intelligence. In 1950, Turing published 'Computing Machinery and Intelligence', in which he proposed what is now called the Turing Test: if a machine can carry on a conversation that is indistinguishable from a human conversation, it should be considered to think. This question — can machines think? — is still at the centre of artificial intelligence research today. The Pilot ACE was used for practical work at the NPL: calculating stresses on aeroplane fuselages, working out ballistic trajectories, and other scientific and engineering problems. A commercial version, called DEUCE, was sold by the English Electric Company. More than 30 were sold. Turing's design influenced computers in Britain and America for a decade. Why does it matter that the person who designed something was not there when it worked?

Points to consider (for the teacher)

Because it is typical of how invention actually works. Very few inventors see their ideas fully realised. Many do work that is taken up by others. Some are pushed out of projects before completion. Some are not credited. Some never know the full impact of what they made. Turing's case is unusually clear: he designed the ACE, which became the Pilot ACE, which influenced the DEUCE, which influenced later British computing. The line of descent is traceable. But Turing did not operate the machine. He did not see the commercial success. He was 41 when he died. Students should see that the history of technology is full of people whose contributions were larger than their recognition. Turing is the most prominent example in British computing history, but not the only one. Women who worked at Bletchley Park, engineers who built the Pilot ACE, and the mathematicians who worked alongside Turing all played essential roles that history has largely forgotten.

4

In January 1952, Alan Turing reported a burglary at his home in Manchester. During the police investigation, it emerged that Turing had been in a relationship with a man. Homosexuality was a criminal offence in Britain under the 1885 Criminal Law Amendment Act. Turing was arrested. He did not deny the relationship. He did not think he had done anything wrong. He was prosecuted and convicted of 'gross indecency'. The judge offered him a choice: prison or probation with hormone treatment — synthetic oestrogen injections designed to suppress sexual drive. Turing chose the treatment. The hormone treatment lasted a year. It caused physical changes to Turing's body. He kept working, travelling to Europe for academic conferences, and corresponding with colleagues. But those who knew him at the time say he was deeply changed. On 8 June 1954, Turing was found dead in his home. He was 41. There was a half-eaten apple beside his bed. The inquest recorded suicide by cyanide poisoning. Some people have since questioned whether it was truly suicide. No investigation has changed the official finding. The British government issued a formal apology for the treatment of Turing in 2009. In 2013, he received a royal pardon. From 2017, the 'Alan Turing Law' posthumously pardoned thousands of men convicted under the same law. From 2021, his face appeared on the British fifty-pound note. What does it mean when a state celebrates someone it destroyed?

Points to consider (for the teacher)

This is the question the lesson ends on, and it has no comfortable answer. The apology, the pardon, the banknote, the law named after him — these are real things that have real effects, particularly for gay men who were still alive and still carried criminal records. The Turing Law specifically helped living people. At the same time, none of it restored what was taken from Turing: the years of health, the work he might have done, the life he might have lived. Celebration after death is not the same as justice during life. Students should think about the difference between commemorating an injustice and repairing it. This connects to wider questions about how societies deal with historical wrongs: formal apologies, pardons, reparations, memorials. None of these are the same as having done right in the first place. The lesson should end on this note: the Pilot ACE is a beautiful and important machine. Alan Turing is a genuine hero of science. Both of these things are true at the same time as the fact that the British state prosecuted him, forced harmful treatment on him, and drove him to his death at 41. Students should be able to hold all of this at once.

What this object teaches

The Pilot ACE (Pilot Automatic Computing Engine) is one of the world's earliest general-purpose stored-program computers. It was built at the National Physical Laboratory in London in 1950, based on the design of Alan Turing. When first operated, it was the fastest computer in the world. It is now the oldest complete general-purpose computer surviving anywhere. Alan Turing (1912-1954) was the mathematician who designed the theoretical basis of computing in 1936, led the code-breaking work at Bletchley Park that helped win World War Two, and designed the ACE computer. In 1952, Turing was prosecuted under British law for having a relationship with another man. He was convicted and subjected to chemical castration as an alternative to prison. He died in 1954 at the age of 41. The British government issued a formal apology in 2009. A royal pardon followed in 2013. From 2017, thousands of men prosecuted under the same laws have been posthumously pardoned under legislation informally known as the Alan Turing Law. Since 2021, Turing's face has appeared on the British fifty-pound note.

Year	What Turing did	What the state did
1936	Published paper on computable numbers, defining the theoretical basis of computing	Nothing — the paper was not widely understood
1939-1945	Led code-breaking work at Bletchley Park; broke Enigma; helped shorten World War Two	Classified his work under the Official Secrets Act; gave no public recognition
1945-1948	Designed the ACE computer at the National Physical Laboratory	Moved slowly on building it; Turing left in frustration
1950	Pilot ACE built and run (in his absence); published the Turing Test paper	Pilot ACE completed; no major recognition for Turing
1952	Reported a burglary; relationship with a man revealed	Arrested and prosecuted for homosexuality; convicted; forced hormone treatment
1954	Died aged 41	Inquest recorded suicide; no official response
2009-2021	(Posthumous)	Formal apology (2009); royal pardon (2013); Turing Law pardoning others (2017); face on fifty-pound note (2021)

Key words

Stored-program computer

A computer that stores its instructions (the program) in the same memory as its data. This means the program can be changed without rebuilding the machine. Turing's design was one of the earliest practical implementations of this idea.

Example: Before stored-program computers, calculating machines had to be physically rewired or reconfigured to change what they did. A stored-program computer can run a different program just by loading new instructions — the same principle as software on modern computers.

Enigma

A German encoding machine used during World War Two to encrypt military communications. The code changed every day. Alan Turing led the mathematical work that broke the Enigma code at Bletchley Park.

Example: The Bombe machine that Turing designed could test millions of possible Enigma settings quickly. The information gained from reading German communications helped the Allies make military decisions throughout the war.

Turing Test

A test for artificial intelligence proposed by Alan Turing in 1950. If a machine can have a conversation that is indistinguishable from a human conversation, Turing argued, it should be considered to think.

Example: The Turing Test is still discussed in artificial intelligence research today. Modern AI systems like large language models have revived debate about what it means to 'pass' the test and whether passing it would actually prove intelligence.

Chemical castration

A treatment using hormones to suppress sexual drive. In Turing's case, this meant injections of synthetic oestrogen. It was offered as an alternative to prison under British law in 1952.

Example: The treatment caused physical side effects including changes to Turing's body. It was not a cure for anything — homosexuality is not an illness — but a punishment imposed through the criminal justice system.

Alan Turing Law

An informal name for a 2017 amendment to British law that posthumously pardoned men convicted of homosexual acts that are no longer offences. It also allowed living men with such convictions to apply for pardons.

Example: The law is named after Turing but covers thousands of other men prosecuted under the same laws. It represents a formal acknowledgement by the state that these prosecutions were wrong.

Vacuum tube (thermionic valve)

An electronic component used in early computers to perform calculations. Vacuum tubes can switch between on and off states very fast, allowing binary arithmetic. The Pilot ACE used fewer than 1,000. Later computers used fewer tubes as transistors replaced them from the late 1950s.

Example: Vacuum tubes were fragile, produced heat, and sometimes burned out unexpectedly. One of the big advances in computing was the transistor, invented in 1947, which was smaller, faster, and more reliable.

Use this in other subjects

Mathematics: Discuss binary arithmetic: how computers perform all calculations using only 0 and 1. Have students try converting small decimal numbers to binary. Connect this to Turing's theoretical work on what kinds of problems can be expressed as rules a machine can follow.
History: Build a timeline of World War Two alongside a timeline of computing development. Place Turing's Bletchley Park work, the end of the war, the design of the ACE, and the Pilot ACE on both. Discuss: how did war accelerate computing? How did computing shape the war?
Citizenship: Discuss how laws can be unjust. The law that prosecuted Turing was not repealed until 1967. Men prosecuted under it were not posthumously pardoned until 2017. Discuss: what obligations does a state have when its laws are later recognised as unjust? What forms can acknowledgement take?
Ethics: Discuss the concept of justice delayed being justice denied. Turing was pardoned 59 years after his death. His face is on a banknote. Does posthumous recognition repair historical injustice? What would genuine repair look like?
Science: Discuss how computers work at a basic level: binary arithmetic, memory, the stored-program concept. Connect the physical components of the Pilot ACE (vacuum tubes, mercury delay lines) to modern equivalents (transistors, RAM). Discuss: why did computing advance so quickly after 1950?
Language: Read Turing's 1950 paper 'Computing Machinery and Intelligence', which opens with the question: 'Can machines think?' Discuss what Turing meant by this and how the question has changed since 1950. Connect to contemporary discussions about artificial intelligence.

Common misconceptions

Wrong

Alan Turing invented the computer.

Right

No single person invented the computer. Turing made essential theoretical contributions and designed important early computers. Other people — including Charles Babbage (earlier theoretical work), Konrad Zuse (first programmable computer, 1941), John Mauchly and J. Presper Eckert (ENIAC, 1945), and the team at Manchester University — all made essential contributions. Turing's work was foundational, not solely responsible.

Why

The myth of the lone inventor hides how technology actually develops: through many people's work over time.

Wrong

Turing personally broke the Enigma code during the war.

Right

Breaking Enigma was the work of a large team at Bletchley Park — mathematicians, linguists, engineers, and many others, including many women in key roles. Turing led important parts of the mathematical work and designed the Bombe machine. He was one of many essential contributors, not the only one.

Why

Simplifying the Bletchley Park story to a single heroic figure erases the contributions of many others, particularly women whose roles are now being better recognised.

Wrong

Turing's treatment was unusual and Britain quickly recognised it as wrong.

Right

Turing was one of thousands of men prosecuted under the same laws. Homosexuality remained a criminal offence in Britain until 1967. The formal pardon of Turing came in 2013; broader posthumous pardons for others came in 2017. Recognition took decades. Many men affected by these laws lived and died without acknowledgement.

Why

Presenting Turing's case as uniquely unjust can hide the systematic nature of the persecution. Many others were equally wronged.

Wrong

The Turing Test proves whether a computer is intelligent.

Right

The Turing Test is a proposal for one possible measure of machine intelligence, not a definitive test. Many AI researchers today question whether it measures the right things. A machine could pass the Turing Test without being genuinely intelligent in a meaningful sense, and an intelligent machine might fail it for reasons unrelated to intelligence. The debate about what intelligence actually is and how to measure it is still very much open.

Why

The Turing Test is often presented in popular culture as settled science. It is actually a starting point for a debate that is still going on.

Teaching this with care

This lesson involves the prosecution of a gay man and the specific punishment of chemical castration. Be clear and honest about what happened without being clinical to the point of coldness or detailed to the point of voyeurism. Students need to know what was done, not graphic details of how. Use accurate language: Turing was prosecuted under laws criminalising homosexuality. The treatment was chemical castration using synthetic hormones. He died at 41. The lesson should be taught in a way that honours his humanity, not just his genius. LGBTQ+ students may find this lesson personally significant. Create space for that without putting anyone on the spot. The lesson should make clear that the laws that prosecuted Turing were unjust, and that this injustice was systematic, not exceptional. Thousands of men were affected. Some students may have family members who were affected by similar laws in Britain or other countries. Be aware that laws criminalising homosexuality still exist in many countries today. This is not purely historical. Do not present Turing only as a tragedy. He was a brilliant, productive, and curious person who did extraordinary work until the end of his life. His death was the result of an injustice, but his life was also full of achievement and meaning. Avoid the Imitation Game film as a primary source. It is a widely seen film about Turing but contains significant historical inaccuracies and simplifications. If students have seen it, acknowledge it but correct the record where necessary. Pronounce: Turing ('TYOO-ring'). Enigma ('en-IG-ma'). Bletchley Park ('BLECH-lee'). End the lesson on the present: the Turing Test is still debated. The questions Turing asked about machine intelligence are being asked again by AI researchers. The law named after him has helped living people. His face is on the banknote in your pocket if you are in Britain. The story is not finished.

Check what students have understood

Answer each question in one or two sentences. Use what you have learned about the Pilot ACE and Alan Turing.

What is the Pilot ACE and why is it historically important?

The Pilot ACE is one of the world's earliest general-purpose stored-program computers. It was built at the National Physical Laboratory in London in 1950, based on Alan Turing's design. It was the fastest computer in the world when first operated and is the oldest complete general-purpose computer surviving anywhere today.

Marking note: Award full marks for any answer that identifies it as an early stored-program computer and notes its historical significance. The 'oldest surviving' detail is a bonus.
What was Alan Turing's contribution to World War Two?

Turing led the mathematical work at Bletchley Park that broke the German Enigma code. He designed the Bombe machine that could find the daily Enigma settings. Breaking Enigma allowed the Allies to read German military communications. Historians believe this may have shortened the war by years and saved millions of lives.

Marking note: Award full marks for any answer that mentions Bletchley Park, Enigma, and some sense of the impact. Note to teacher: Turing was one of a large team; credit full marks even if the student does not mention the team.
What happened to Alan Turing in 1952 and why?

In 1952, Turing was arrested and prosecuted for having a relationship with another man. Homosexuality was a criminal offence in Britain at the time under the 1885 Criminal Law Amendment Act. He was convicted and given a choice between prison and hormone treatment. He chose the hormone treatment, a form of chemical castration.

Marking note: Award full marks for any answer that clearly states the nature of the prosecution (homosexuality being illegal) and the punishment. Either the prosecution or the punishment alone earns partial marks.
What is the Turing Test?

The Turing Test, proposed by Turing in 1950, is a test for machine intelligence. If a machine can have a conversation that is indistinguishable from a human conversation, Turing argued it should be considered to think. The test is still discussed in artificial intelligence research today.

Marking note: Award full marks for any answer that captures the core idea: a machine that can fool a person into thinking it is human could be considered intelligent. The ongoing debate is a bonus.
What forms of recognition has Britain given Turing since his death? Does this amount to justice?

Britain gave a formal apology from the Prime Minister in 2009, a royal pardon in 2013, and in 2017 passed the Alan Turing Law pardoning thousands of men prosecuted under the same laws. From 2021, Turing's face appeared on the fifty-pound note. Whether this amounts to justice is debatable: it acknowledges the wrong but cannot restore what was taken from him.

Marking note: Award full marks for listing at least two forms of recognition and making some attempt to reflect on whether they amount to justice. The lesson deliberately leaves this as an open question.

Discuss together

These questions have no single right answer. Talk in pairs or small groups, then share your ideas with the class.

Turing helped save millions of lives during World War Two, and the state that benefited from his work later prosecuted him. How should we think about a state that does this?

Push students beyond simple condemnation. The state that prosecuted Turing in 1952 was not the same government as the one that employed him at Bletchley Park. Laws and societies change over time, sometimes slowly and badly. The same state also provided Turing's salary, the resources to build the Pilot ACE, and eventually issued an apology. How do we judge institutions that do both good and terrible things? Strong answers will see that states are not single entities with consistent moral character — they are made up of laws, institutions, and people that change over time. The better question is not whether this state was bad, but what conditions led to the prosecution, whether those conditions still exist, and what obligations arise when injustice is recognised.
Turing's face is now on the British fifty-pound note. Is this an appropriate way to remember him? What does putting someone on a banknote say?

This is a question about the politics of commemoration. Arguments for: it is a major form of public recognition, seen by millions of people, signalling that his contribution is valued; it pairs with the apology and the pardon as a formal act of acknowledgement. Arguments against: putting someone on a banknote is a form of national appropriation — it makes Turing a symbol of British achievement while obscuring what Britain did to him; it is a kind of washing away of guilt through celebration; the people who prosecuted him are not named or remembered. Strong answers will see both sides. End by asking: whose faces are on banknotes in your country, and what does that choice say about what the country values?
Turing asked in 1950: can machines think? In 2026, with AI systems that can write, draw, and have conversations, how would you answer his question?

This is the forward-looking question the lesson ends on. There is no single right answer. Push students to define what they mean by 'think'. If thinking means processing information and producing outputs, modern AI clearly does it. If thinking means consciousness, self-awareness, understanding, or experiencing the world, the question is much harder. Turing's test was specifically about conversation, not consciousness. Modern AI systems can pass versions of the Turing Test but we have no idea whether they are conscious or understand anything. End by noting that this is one of the most important scientific and philosophical questions of the twenty-first century. The question Turing asked in 1950 is more urgent now than ever. Students are living through the period when some kind of answer may begin to emerge.

Teaching sequence

THE HOOK (5 min)

Without saying anything about the lesson, ask: 'Can you think of a job that someone might do that saves millions of lives but that almost nobody knows about?' Take guesses. Then say: 'During World War Two, a mathematician broke a secret code that historians think shortened the war by years and saved millions of lives. His work was classified. Nobody knew. And later, the government he worked for prosecuted him for who he loved. We are going to find out about him and about the machine he designed.'
INTRODUCE THE OBJECT (10 min)

Describe the Pilot ACE: the machine now in the Science Museum in London, built in 1950, the oldest complete general-purpose computer surviving anywhere. Explain what a stored-program computer is. Show the image. Explain that Turing designed it but was not there when it ran. Pause and ask: 'Why might someone leave a project they had spent years designing?' The answers will lead into the Turing story.
THE CONTRIBUTION AND THE COST (15 min)

Tell the story in two parallel threads. On the board, draw two columns: WHAT TURING DID and WHAT THE STATE DID. Fill them in together: 1936 paper on computing, Bletchley Park and Enigma (state: classified), ACE design (state: slow and dismissive), Pilot ACE runs (state: no recognition), 1952 prosecution, hormone treatment, death. Stand back and ask: 'What do you notice about these two columns?' The gap between contribution and treatment should be clear and stark.
THE AFTERWARDS (10 min)

Explain the posthumous recognition: the 2009 apology, the 2013 pardon, the 2017 Turing Law, the 2021 banknote. Ask: 'Does this amount to justice?' Take honest answers. Do not resolve it. Ask: 'What would genuine justice have looked like, at the time?' This is the harder question.
CLOSING (5 min)

Ask: 'In 1950, Turing asked: can machines think? How would you answer that question today?' Take a few honest answers. End by saying: 'The Pilot ACE is a machine made of vacuum tubes and mercury and wire. It is also the physical beginning of everything you use today: every phone, every computer, every search engine. The man who designed it asked questions we are still trying to answer. He deserved better than he got. The machine outlasted him by decades. It is still there, in London, if you want to see it.'

Classroom materials

Two Columns

Instructions: Students draw two columns on a piece of paper, headed CONTRIBUTION and TREATMENT. Working from information given in the lesson, they fill in Turing's contributions (1936 paper, Bletchley Park, Enigma, ACE design, Turing Test) alongside what was done to him (secrecy, slow project, prosecution, hormone treatment, death at 41). When both columns are full, students write one sentence at the bottom: 'The gap between these two columns teaches us...' Share sentences and discuss.

Example: In one class, the sentences ranged from 'that governments are sometimes unjust' to 'that being brilliant does not protect you from prejudice' to 'that we only celebrate people after it is too late to help them'. The teacher said: 'All of these are true. The gap you have drawn is real. It happened to a real person. It happened to thousands of others too. What the lesson asks you to do is not just feel sad about it, but think about what conditions made it possible and whether those conditions still exist anywhere in the world today.'

The 1950 Question

Instructions: Read students the opening lines of Turing's 1950 paper: it asks the question 'Can machines think?' Students write a one-paragraph answer to this question, today, in 2026, taking into account what they know about AI. Answers should define what they mean by 'think' and give at least one reason for their position. Share and discuss. What would Turing think of AI today?

Example: In one class, students gave wildly different answers. One said: 'Machines can process but not understand. Thinking needs understanding.' Another said: 'If it acts like it thinks and nobody can tell the difference, the difference does not matter.' A third said: 'We do not even fully understand what thinking is in humans. We cannot know if machines do it.' The teacher said: 'You have just participated in one of the oldest live debates in computer science. Turing asked the question in 1950. He died four years later. He never saw what his question would produce. We are the people who have to try to answer it.'

Recognition and Justice

Instructions: Present students with four forms of posthumous recognition given to Turing: the 2009 apology, the 2013 pardon, the 2017 Turing Law, and the 2021 fifty-pound note. Ask students to rank these from most meaningful to least meaningful, with a reason for each ranking. Then ask: is any of these justice? What would justice have actually looked like? Share rankings and discuss.

Example: In one class, most students ranked the Turing Law highest because it helped living people, not just Turing. The apology came second. The banknote came last because, as one student said: 'It makes him a brand.' The discussion that followed was about the difference between commemoration and repair. The teacher said: 'What you have noticed is something that politicians and historians debate seriously. When a state has done wrong, what does it owe? An apology? Money? Changed laws? The answer is probably all of these, and the debate is about which matters most and whether any of it is enough.'

Where to go next

Try a lesson on the Antikythera Mechanism for another case where a brilliant object outlasted the person or people who made it, and where the full significance was only understood later.
Try a lesson on the Berlin Wall piece for another object connected to the histories of persecution and the moment when those histories changed.
Connect this lesson to mathematics class with a project on the history of computing: Babbage, Lovelace, Turing, von Neumann, and the many people whose contributions are less celebrated.
Connect this lesson to citizenship class with a discussion of laws that have been recognised as unjust and the forms of redress that states can offer. Compare Turing's case to others.
Connect this lesson to science class with a project on how artificial intelligence works today, and how it relates to Turing's original questions about machine intelligence.
Connect this lesson to contemporary news and technology: students research current AI systems and debate whether any of them come close to passing the Turing Test in a meaningful sense.

Key takeaways

The Pilot ACE is one of the world's earliest general-purpose stored-program computers, built in 1950 at the National Physical Laboratory in London based on Alan Turing's design. It is now in the Science Museum in London and is the oldest complete computer of its kind surviving anywhere.
Alan Turing (1912-1954) was the mathematician who defined the theoretical basis of computing in 1936, led the Enigma code-breaking work at Bletchley Park that helped win World War Two, and designed several early computers.
In 1952, Turing was arrested and prosecuted under British law for having a relationship with another man. He was convicted and subjected to chemical castration as an alternative to prison. He died in 1954 aged 41.
Turing's wartime work was classified. He received no public recognition during his lifetime. The full story was not made public until the 1970s.
Britain issued a formal apology in 2009, a royal pardon in 2013, and legislation posthumously pardoning thousands of men prosecuted under the same laws in 2017. Turing's face appeared on the fifty-pound note from 2021.
The Turing Test, proposed in 1950, asks whether a machine that can hold a conversation indistinguishable from a human conversation should be considered to think. It is still debated in artificial intelligence research today.

Sources

Alan Turing: The Enigma — Andrew Hodges (1983) [academic]
Pilot ACE — Science Museum Collection — Science Museum, London (2024) [institution]
Computing Machinery and Intelligence — Alan Turing (1950) [academic]
The Turing Law: Posthumous Pardons for Gay Men — UK Government (2017) [institution]
Bletchley Park: Code-Breaking and the Road to Victory — Sinclair McKay (2010) [academic]

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The Pilot ACE: The Computer That Turing Built — and the Man the State Destroyed

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