Thousands of people have signed a Downing Street petition calling for a posthumous government apology to World War II code breaker Alan Turing.

Writer Ian McEwan has just backed the campaign, which already has the support of scientist Richard Dawkins.

In 1952 he was prosecuted under the gross indecency act after admitting to a sexual relationship with a man. Two years later he killed himself.

The petition was the idea of computer scientist John Graham-Cumming.

He is seeking an apology for the way the young mathematician was treated after his conviction. He has also written to the Queen to ask for a posthumous knighthood to be awarded to the British mathematician.

Alan Turing was given experimental chemical castration as a "treatment" and his security privileges were removed, meaning he could not continue work for the UK Government Communications Headquarters (GCHQ).

"This added insult and humiliation ultimately drove him to suicide," said Peter Tatchell. "With Turing’s death, Britain and the world lost one of its finest intellectual minds. A government apology and posthumous pardon are long overdue."

National legacy

Alan Turing is most famous for his code-breaking work at Bletchley Park during WWII, helping to create the Bombe that cracked messages enciphered with the German Enigma machines.

However he also made significant contributions to the emerging fields artificial intelligence and computing.

In 1936 he established the conceptual and philosophical basis for the rise of computers in a seminal paper called "On Computable Numbers" whilst in 1950 he devised a test to measure the intelligence of a machine. Today it is known as the Turing Test.

After the war he worked at many institution including the University of Manchester, where he worked on the Manchester Mark 1, one of the first recognisable modern computers.

There is a memorial statue of him in Manchester’s Sackville Gardens which was unveiled in 2001.

"I kept reading about potential funding cuts at Bletchley Park and I suddenly felt really mad about it," said Mr Graham-Cumming.

"I felt Turing was getting overlooked as being a British genius and that there was a blindspot in the public eye about an important man."

He has so far collected more than 5,500 signatures.

He admits that an official apology to Alan Turing is "unlikely", as Mr Turing has no known surviving family, but he says that the real aim of the petition is symbolic.

"The most important thing to me is that people hear about Alan Turing and realise his incredible impact on the modern world, and how terrible the impact of prejudice was on him," he said.

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