After a high-profile campaign supported by tens of thousands of people around the world, Alan Turing has been granted a pardon under the Royal Prerogative of Mercy.

The centenary of Alan Turing's birth in 2012 celebrated him as "father of computer science" and for his achievements as World War II Bletchley Park codebreaker, but also drew attention to the treatment meted out to him for a homosexuality.

Turing was convicted for "gross indecency" at a time when homosexual acts were illegal in the UK and as part of his sentence underwent chemical castration. Two years later he died from cyanide poisoning, at the age of 41, apparently having committed suicide.

Pardons are usually only granted when a person is innocent of the offence and previous attempts to achieve a pardon for Turing had had limited success. In 2009 the British Prime Minister, Gordon Brown, issued an apology for Turing's treatment, but let the conviction stand and in February 2012 Justice Minister Lord McNally explaining why a the petition for his pardon was being denied said:

"A posthumous pardon was not considered appropriate as Alan Turing was properly convicted of what at the time was a criminal offense".

Now a year after a group of prominent scientists and peers of the realm sent an open letter to:

urge the Prime Minister formally to forgive this British hero, to whom we owe so much as a nation whose pioneering contribution to computer sciences remains relevant even today

a petition to Government signed by more 37,000 people and a debate in the House of Lords in which peers of all political persuasion gave speeches in favour of the pardon, it has finally been granted and came into effect on December 24th, 2013.

Announcing it, Justice Secretary Chris Grayling said:

“Dr Turing deserves to be remembered and recognized for his fantastic contribution to the war effort and his legacy to science. A pardon from the Queen is a fitting tribute to an exceptional man.”