Alan Turing: The father of modern computing credited with saving millions of lives

Maths genius killed himself at just 41 after being convicted under Victorian anti-homosexual laws – but will now be new face of £50 note

When he was just nine years old, Alan Turing’s headmistress at St Michael’s Primary School in Hastings wrote a report to his parents. “I have had clever boys and hard-working boys,” she noted. “But Alan is a genius.”

If anything, her words turned out to be an understatement. The man who will appear on the new £50 note was one of the most gifted scientists, mathematicians and thinkers of his – or any other – age. Among his achievements were developing the theoretical underpinning of the world’s first computers and laying the groundwork for the development of artificial intelligence.

His most famous work, cracking the fiendishly complex Nazi Enigma code during the Second World War, is said to not only have turned the conflict in favour of the allies but done so with such significance that it shortened the whole thing by several years. Some military historians estimate Turing’s genius saved as many as two million lives.

Yet his life would end in tragedy. After reporting a burglary at his Manchester home in 1952, police charged Turing himself with gross indecency when he admitted, in good faith, he was in a relationship with another man.

He was chemically castrated, barred from continuing to work with GCHQ, and had his heroism during the Second World War all but scrubbed from records. He died two years later, aged just 41 and a convicted criminal, after eating an apple laced with cyanide.

Now, 65 years on, his appearance on the banknote will perhaps be seen as the completion of a rehabilitation that should never have been necessary.

Turing was born in London in 1912. His headmistress in Hastings was not the only teacher who saw his potential. The word “genius” was also used in a report from his secondary, Sherborne School in Dorset, when he was 13. After studying mathematics at the University of Cambridge, he went on to acquire his PhD at Princeton University, in New Jersey in the US.

It was while there that he developed the notion of a “universal computing machine” which could solve complex calculations. This would become known as the Turing machine, an invention largely seen as the father of the digital computer. He returned to Britain at the outset of war in 1939 and joined GCHQ, leading a team of codebreakers at the now famous Bletchley Park complex in Buckinghamshire.

There, he and his team managed to mimic the operations of the infamous German Enigma machine in order to break its codes. Crucially, the information provided allowed the allies to locate German U-boats, giving them a significant strategic advantage at sea, thus, turning the war in the allies’ favour.

Other Nazi codes were cracked too, leaving vast quantities of the enemy’s communications open to the allies. “We were using Turingery [a code-breaking technique] to read what Hitler and his generals were saying to each other over breakfast,” explained Jerry Roberts, a one-time captain at Bletchley Park, in 2012.

Postwar, Turing’s fascination with computers led him Manchester University where he produced his most famous paper, Computing Machinery and Intelligence, in which he devised what he called the Imitation Game – now named the Turing Test – a method to determine whether a machine showing behaviour can truly be called intelligent.

It was also here that he started to explore the homosexual identity he had largely – though far from entirely – kept hidden until then. A relationship with a 19-year-old called Arnold Murray was to lead to his downfall following the burglary in 1952.

Murray told Turing he knew the thief’s identity, which Turing passed on to detectives. They, however, took it on themselves, under Victorian anti-homosexuality laws, to charge Turing and Murray for gross indecency. Apparently scarred by the conviction – and his resulting chemical castration – Turing is said to have laced an apple with cyanide and eaten half of it in 1954.

It was not until 2009 that the British government apologised for his treatment, and not until 2013 that he was pardoned by the Queen. Yet his legacy now appears assured for all time.

As well as statues in Bletchley Park and Manchester (fittingly, located halfway between the city’s gay village and the university’s science department) and his place on the new £50 note, a more subtle tribute may be seen by millions of us every day: although Steve Jobs never confirmed the theory, it is widely believed Apple was named partially in tribute to Turing – fighter of fascism and father of the computer age.