Family of Alan Turing seeking pardons for 49,000 men prosecuted for homosexuality
A handout picture released by Sherborne School on June 22, 2012 shows British mathematician Alan Turing in school in Dorset, southwest England, aged 16 in 1928 (AFP)

Relatives of wartime codebreaker Alan Turing, subject of Oscar-winning film "The Imitation Game", will on Monday hand in a petition calling for the pardoning of 49,000 men prosecuted like him for homosexuality.

Nearly half a million people signed the petition via website

Turing's great-nephew Nevil Hunt, his great-niece Rachel Barnes and her son Thomas, are scheduled to deliver the petition to 10 Downing Street.

Turing, whose work on deciphering the German Enigma codes led to a vital breakthrough in the war against the Nazis, was convicted in 1952 for gross indecency with a 19-year-old man.

He was chemically castrated and two years later died from cyanide poisoning in an apparent suicide.

Turing received a posthumous royal pardon in 2013 and now campaigners want authorities to pardon all men convicted under the law before homosexuality was legalised in 1967.

Barnes from Taunton, said: "I consider it to be fair and just that everybody who was convicted under the Gross Indecency Law is given a pardon. It is illogical that my great uncle has been the only one to be pardoned when so many were convicted of the same crime.

"I feel sure that Alan Turing would have also wanted justice for everybody."

The editor of Attitude Magazine, Matthew Todd, who will also visit Downing Street, said: "Generations of gay and bisexual men were forced to live their lives in a state of terror.

"Men convicted of gross indecency were often considered to have brought huge shame on their families and many took their own lives. We still live with the legacy of this period today and it's about time the country addressed this appalling part of our history."

Benedict Cumberbatch's Oscar-nominated portrayal of Turing has brought the pioneering scientist's story to a wider audience.

"The Imitation Game" was nominated in eight Oscar categories and at Sunday night's ceremonies in Hollywood won the award for Best Adapted Screenplay.

Turing led a team decoding messages at Bletchley Park and designed the machine which decrypted German messages, but the work remained secret until many years after the war's end.

The team's work helped shorten the conflict and saved many thousands of lives.

The film follows Turing from his days as a Second World War code breaker at Bletchley Park to his work at Manchester University, where he was hailed as the father of modern computing, and his tragic death.