Alan Turing

The Boy Who Thought Differently

Alan Mathison Turing was born on the 23rd of June 1912 in Maida Vale, London. His parents were civil servants posted to India, and young Alan spent much of his childhood boarding in England while they were overseas. He was, by most accounts, a strange child. Brilliant, obviously, but strange. He taught himself to read in three weeks. His teachers noted his obsession with numbers and science but complained that he neglected his Latin.

At Sherborne School in Dorset, he was the classic misfit. Too clever for his classmates, too unconventional for his teachers. He formed a deep friendship with Christopher Morcom, a fellow pupil who shared his love of science. When Morcom died suddenly of bovine tuberculosis in February 1930, it devastated the 17-year-old Turing. He later wrote to Morcom's mother that he wanted to believe that Christopher's mind lived on, that it could exist independently of the body. It was the kind of question that would shape everything he did next.

In 1931, he went up to King's College, Cambridge, to study mathematics. By 1935, at the age of 22, he was elected a Fellow of King's for a dissertation on the central limit theorem. A year later, he published "On Computable Numbers," a paper that laid the theoretical foundation for every computer that has ever existed. In it, he described an imaginary machine that could solve any problem capable of being expressed as an algorithm. It became known as the Turing Machine, and it is still the fundamental concept behind how computers work.

He went to Princeton in 1936 to study under Alonzo Church, earning his PhD in 1938. He could have stayed in America. Princeton offered him a position. But he came home. Within a year, Britain was at war.

Bletchley Park: The War Nobody Talked About

On the 4th of September 1939, the day after Britain declared war on Germany, Alan Turing reported to Bletchley Park in Buckinghamshire. He was 27 years old. He was assigned to Hut 8, the section responsible for breaking German naval Enigma, the encryption system protecting communications between U-boats and their command.

The Enigma machine was considered unbreakable. It had approximately 159 million million million possible settings. Every day at midnight, the settings changed. Every day, the codebreakers had to start again from scratch.

Turing, working with Gordon Welchman, designed the Bombe, an electromechanical machine that could test Enigma settings at speed. Welchman's contribution was the diagonal board, a crucial enhancement that made the whole thing work. The first Bombe, called "Victory," was installed in March 1940. By 1943, there were over 200 of them running around the clock.

Breaking naval Enigma was the hardest problem at Bletchley. The naval version used a four-rotor machine, more complex than the three-rotor Army and Air Force versions. Turing developed a technique called Banburismus that allowed codebreakers to eliminate vast numbers of possible settings before running the Bombes. It was painstaking, probabilistic, and brilliant. It worked.

The intelligence produced at Bletchley Park, codenamed Ultra, is estimated to have shortened the war by at least two years. The Battle of the Atlantic, the fight to keep Britain's supply lines open against the U-boat threat, may well have been lost without it. Churchill called the Bletchley Park staff "the geese that laid the golden eggs and never cackled." Turing was the most important goose of all.

After the war, he was awarded an OBE. He could never tell anyone what it was for. The work at Bletchley remained classified for decades.

Manchester: Building the Future on Oxford Road

In September 1948, Alan Turing arrived at the University of Manchester as a Reader in the Mathematics Department. His old Bletchley Park colleague Max Newman had been appointed to lead the university's new Computing Machine Laboratory, and Newman wanted Turing.

Two months earlier, on the 21st of June 1948, two engineers called Tom Kilburn and Freddie Williams had run the world's first stored-program computer in a lab on Oxford Road. It was called the Manchester Baby, and it proved that a machine could store and execute its own instructions. Turing didn't build the Baby. Kilburn and Williams did that. But the theoretical work that made it possible, the idea of a universal machine that could be programmed to do anything, that was Turing's. The paper he had published in 1936, twelve years before the Baby ran, was the blueprint.

At Manchester, Turing threw himself into the practical side of computing. The Baby evolved into the Manchester Mark 1, and then into the Ferranti Mark 1, delivered in February 1951, the first commercially available general-purpose computer. Turing wrote its programming manual, the first of its kind ever produced. He designed input systems and worked on the software that would make these enormous machines useful.

But Turing's mind was never content with one problem. In October 1950, while working on the Mark 1, he published a paper in the journal Mind called "Computing Machinery and Intelligence." It opened with a question that changed philosophy: "I propose to consider the question, 'Can machines think?'" The paper proposed what became known as the Turing Test, the idea that a machine could be considered intelligent if a human interrogator could not distinguish its responses from those of a real person. Every conversation you have ever had with a chatbot, every debate about artificial intelligence, every argument about whether machines can truly think, traces back to that paper, written at a desk in Manchester.

Then, in 1952, he published "The Chemical Basis of Morphogenesis" in the Philosophical Transactions of the Royal Society. In it, he used mathematical models to explain how patterns form in nature: the stripes on a zebra, the spots on a leopard, the arrangement of petals on a flower. A computer scientist explaining biology with mathematics. It was decades ahead of its time. Modern researchers are still proving him right.

The Country He Saved Destroyed Him

Alan Turing was gay. In 1950s Britain, that was a criminal offence.

In January 1952, Turing's house in Wilmslow was burgled. He reported it to the police. During the investigation, he told officers about his relationship with a man called Arnold Murray, who he believed knew the burglar. Turing did not hide it. He did not seem to think he had anything to hide. The police disagreed.

Both Turing and Murray were charged with gross indecency under Section 11 of the Criminal Law Amendment Act 1885, the same law that had been used to prosecute Oscar Wilde in 1895. On the 31st of March 1952, Turing pleaded guilty. He was given a choice: prison, or probation with chemical castration. He chose the hormones.

The treatment was diethylstilbestrol, a synthetic oestrogen injected over the course of a year. It rendered him impotent and caused him to develop breast tissue. His security clearance was revoked. The man who had helped win the war, who had laid the theoretical foundations of computing, who was doing some of the most important scientific work in the world, was now considered a security risk because of who he loved.

He continued working at Manchester. He continued running. He continued thinking. But something had changed. His friends noticed it. The hormones, the public humiliation, the loss of his security clearance, all of it weighed on him.

An Apple and a Bench

On the 8th of June 1954, Turing's cleaner found him dead at his home in Wilmslow. He was 41 years old. There was a half-eaten apple beside his bed. The post-mortem found cyanide poisoning. The inquest ruled it suicide.

His mother Sara never accepted that verdict. She pointed out that Turing kept chemicals in his house for electroplating experiments and was famously careless with them. The apple was never tested for cyanide. Historian Jack Copeland has argued that the evidence does not support the suicide conclusion and that accidental poisoning is at least equally plausible. We will probably never know for certain what happened that night in Wilmslow.

What we do know is what came after. For decades, nothing. Silence. The Official Secrets Act kept Bletchley Park classified. The computer revolution he had helped launch was credited to others. His conviction stood on the record. His story was barely told.

Then, slowly, Manchester started to remember.

In 2001, a bronze statue was unveiled in Sackville Gardens, in the heart of Manchester's Gay Village. It was sculpted by Glyn Hughes and paid for by a public appeal of around £16,000, started by a Stockport barrister called Richard Humphry after he saw the play Breaking the Code. The statue shows Turing sitting on a bench, holding an apple, looking out across the gardens. It was unveiled on the 23rd of June, what would have been his 89th birthday.

On Christmas Eve 2013, Queen Elizabeth II granted Alan Turing a royal pardon, 61 years after his conviction. In 2017, the "Alan Turing law," part of the Policing and Crime Act, provided automatic posthumous pardons to all men convicted under the historical laws that had criminalised homosexuality in England and Wales.

The building where he worked at the University of Manchester is now the School of Computer Science. The institute that carries his name, the Alan Turing Institute, is the UK's national centre for data science and artificial intelligence. His face has been on the £50 note since 2021.

But the best memorial is the simplest one. A man sitting on a bench in a park in Manchester, holding an apple, thinking about the future. Every device you have ever used, every calculation a computer has ever made, every question anyone has ever asked a machine, leads back to him. He saw plenty that needed to be done, and he did as much of it as they let him.

They should have let him do more.