The head of intelligence agency GCHQ has paid tribute to Alan Turing, the brilliant mathematician responsible for cracking the secret wartime codes of Nazi Germany.
In a rare public address, Iain Lobban described Turing as "one of the great minds of the 20th century" whose breakthroughs laid the foundations of the modern information age.
He said that his death at the age of just 41, following a conviction for homosexuality, had been a "loss to the nation".
During the Second World War, Turing worked at the Government Code and Cypher School at Bletchley Park - the forerunner of GCHQ - where he devised the techniques which cracked the German Enigma code.
He is widely seen as the father of computer science and artificial intelligence, and is credited with helping to shorten the course of the war.
But despite his achievements, following war he was prosecuted for homosexuality, which was then illegal, and underwent chemical castration rather than go to prison. He subsequently died of cyanide poisoning - an inquest recorded a verdict of suicide, although his mother and others maintained his death was accidental.
In a speech at Leeds University to celebrate the centenary of his birth, Mr Lobban said Turing's premature death underlined the cost of intolerance.
"We can't rewrite the past. We can't wish mid-twentieth century Britain into a different society with different attitudes," he said. "We can be glad that we live in a more tolerant age. And we should remember that the cost of intolerance towards Alan Turing was his loss to the nation."
Mr Lobban said that he hoped wider appreciation of Turing's achievements would now inspire a new generation of schoolchildren to study science and mathematics.
"Through our eyes, Turing was a founder of the information age: one of the people whose concepts are at the heart of a technological revolution which is as far-reaching as the industrial revolution," he said. "Throughout the post-war era, we continued to enjoy the benefits of the abstract Turing machine model, from our 1980s washing machines to the mini computers we carry in our pockets today. Turing was part of a revolution which has led to a transformation of every aspect of our lives."