My Lords, I join others in congratulating the noble Lord, Lord Sharkey, on the way in which he has introduced his Bill today and his persistence in pursuing this very good cause. It is particularly appropriate that we should be debating this Second Reading just two days after the announcement of Royal Assent to the Marriage (Same Sex Couples) Act—as it were, the ending of a particular chapter of which the Labouchère Act, to which the noble Lord referred, was the shameful beginning. The case that he made for granting a statutory pardon to Alan Turing is compelling, and I wholeheartedly support the Bill.

I am pleased to declare an interest as a trustee of the Science Museum Group, which, as the noble Lord said, has staged an astonishingly successful exhibition called “Codebreaker—Alan Turing’s Life and Legacy”, which has already won first prize in the British Society for the History of Science’s Great Exhibitions competition. It opened on 21 June 2012, and has been visited by many thousands of people. It commemorates the centenary of Turing’s birth by telling the story of how he helped lay the foundations of modern computing and, of course, at Bletchley Park, broke the Enigma codes of the Nazis, which, as everyone now accepts, certainly shortened the Second World War, perhaps by as much as two years. An Enigma machine is indeed on display in the exhibition; it belongs to Sir Mick Jagger, who has kindly lent it for the purpose of the exhibition.

Turing’s first major contribution to science had been a paper written in 1936, when he was just 24, on an abstruse theoretical problem in the philosophy of mathematics. That work brought Turing to the attention of a small group of mathematicians and philosophers, but it was its theoretical description of a universal computing machine, capable of carrying out any computable task, which was later seen as the conceptual basis of today’s stored-program computers.

For Turing, his 1936 universal machines were simply thought experiments, but for others they signalled the future of computing—and the beginning of computing. Turing himself wrote one of the first practical designs for a stored-program computer, later realised as the Pilot ACE, which is on display in the Science Museum exhibition.

Apart from describing Turing’s astonishing achievements in Cambridge, Manchester and Bletchley Park, there is, obviously, some very poignant material about his private life and his shameful treatment at the hands of the state, which, instead of honouring him as a war hero, subjected him to judicial punishment so appalling that it is hard to comprehend, and which indeed is the reason for this Private Member’s Bill today.

Being gay at Cambridge in the 1930s and, indeed, at wartime Bletchley Park, did not seem to be too much of a problem for Turing, but the mood changed in post-war Britain and a new repressive morality emerged. Homosexual people, both men and women, were increasingly characterised as deviant and harmful to the fitness of the race, and their presence in society became a matter of national concern. The Cold War intensified these concerns as gay people were assumed to be at risk of blackmail, thus endangering the security of the nation.

In 1952, following what was then an unlawful sexual relationship, Turing was tried and convicted of gross indecency under Section 11 of the Criminal Law Amendment Act 1885—the same statute, of course, that was used against Oscar Wilde. Turing was stripped of his security clearance and his post-war consultancy to the successor of Bletchley Park, GCHQ, was brought to a sudden end. He was offered the choice of imprisonment or a one-year course of hormone treatment to suppress his libido, and he took the latter. As has been said, it amounted to chemical castration.

On 7 June 1954 he ingested a large amount of cyanide solution at his home in Wilmslow, Cheshire, and was found dead the next day by his housekeeper. The coroner recorded a verdict of suicide, saying that Turing’s mind had become unbalanced. He did not leave a suicide note and the full circumstances of his death are still not known.

Among the more than three-quarters of a million people who have been to see the Codebreaker exhibition at the Science Museum was a group of Members of your Lordships’ House, who made a special visit on 27 November led by the noble Baroness, Lady Trumpington. Being with her in the Codebreaker exhibition was a real privilege—as, indeed, was hearing her speak in this debate today. Winston Churchill described the Bletchley Park cryptanalysts as his “golden geese that never cackled”. I have never considered the noble Baroness as a goose, golden or otherwise, but I am sure that Churchill meant it as a compliment.