Why computing pioneer Alan Turing was prosecuted, pardoned and now will be on 50-pound noteshttps://indianexpress.com/article/technology/science/alan-turing-world-war-ii-hero-prosecuted-for-homosexuality-who-will-be-on-50-pound-notes-5831630/

Why computing pioneer Alan Turing was prosecuted, pardoned and now will be on 50-pound notes

Turing developed a machine to crack German encrypted messages and also came up with a test that was later called the Turing Test. to determine whether machines had acquired intelligence.

Alan Turing note
The concept of the new 50 pound note bearing the image of Second World War code-breaker Alan Turing. (Source: Bank of England via AP)

Codebreaker and computing pioneer Alan Turing has been chosen as the face of Britain’s new 50-pound note that will be issued from 2021, the Bank of England announced Monday. The move has largely been welcomed given the harassment the mathematician faced in his lifetime due to his sexual orientation.

“I hope it will serve as a stark and rightfully painful reminder of what we lost in Turing, and what we risk when we allow that kind of hateful ideology to win,” said John Leech, a former British lawmaker who led the campaign for a pardon for Turing.

The World War II hero

A student of mathematics at the King’s College at the University of Cambridge, Turing graduated with first-class honours and was elected a Fellow of King’s College at just 22, says a profile of him in the British Library. In addition to being a mathematician, he was also a long-distance runner and interested in rowing.

In 1936, Turing travelled to the US to study mathematics at Princeton University and obtained his PhD. It was also when he developed the theory of what would be called a Turing machine, a universal computing machine that could solve complex calculations.


Turing also studied cryptology, in which he studied codes and cyphers that were used to send secret messages. This resulted in him being called to join the British code-breaking organisation which was located at Bletchley Park during World War II.

At Bletchley Park, Turing was part of the team that cracked the ‘Enigma’ code being used by German armed forces to send secret messages to each other. Turing and a fellow code-breaker developed the ‘Bombe’ machine that was used for the purpose.

Turing’s theory was that the code could be hacked by comparing the patterns of the encrypted message with a known portion of plain text to break the code. Turing decided to mechanise the process, and was aided greatly by Gordon Welchman, says the National Museum of Computing.

The first Turing/Welchman machine was known as Agnus Dei, more popularly as Agnes, and became operational in August 1940.

Here’s a video that explains how it works: 

Turing then helped decode encrypted German naval signals in 1941 and in 1942 developed another code-breaking technique called ‘Turingery’ to use against Germans’ new Geheimschreiber (secret writer) encryption machine.

He also developed a secure speech system named Delilah that he claimed could encode voice communications like a telephone scrambler. However, the machine was never used during the war.

After the war, in 1950, he came up with what he called the Imitation Game and later came to be called the Turing Test. It’s a test that is meant to decide whether a machine is intelligent, and whether it can fool humans into believing it isn’t a machine. The test has helped in the development of artificial intelligence and, despite its limitations, remains a test of whether a machine is truly intelligent.

Prosecuted for homosexuality

However, despite being a decorated hero at the end of the War, Turing faced prosecution due to his sexual orientation.

He had reported a burglary at his home in 1952 that revealed his sexual relationship with a 19-year-old man to the police. Due to the anti-homosexuality laws in the UK, Turing was charged with gross indecency and avoided prison by accepting chemical castration. He was given injections of oestrogen intended to neutralise his libido, wrote his biographer.

The conviction under the homosexuality laws also cost him his position at Bletchley Park and his security clearance.

In 1954, he was found dead at home by a cleaner and was said to have died from cyanide poisoning.

The apology

It was in 2009, after a prolonged campaign, that Turing finally received an apology from the UK government.

“The debt of gratitude he is owed makes it all the more horrifying, therefore, that he was treated so inhumanely. In 1952, he was convicted of ‘gross indecency’ – in effect, tried for being gay. His sentence – and he was faced with the miserable choice of this or prison – was chemical castration by a series of injections of female hormones. He took his own life just two years later,” wrote then Prime Minister Gordon Brown.

In 2013, Turing was given a royal pardon for his conviction posthumously.

His life inspired the 2014 film titled The Imitation Game in which Benedict Cumberbatch played the mathematician.

Why is he being put on a 50-pound note? 

Turing is among the Bank of England’s efforts to put images of prominent personalities from various fields on currency notes. The bank had invited suggestions from the public on which scientists should feature on the currency notes, and received around 227,299 nominations.

“Alan Turing was an outstanding mathematician whose work has had an enormous impact on how we live today,” said the Bank of England governor Mark Carney.


“As the father of computer science and artificial intelligence, as well as a war hero, Alan Turing’s contributions were far-ranging and path-breaking. Turing is a giant on whose shoulders so many now stand,” he said.