Hawking defying science to open Paralympics
When Stephen Hawking was diagnosed with motor neurone disease aged 21, he was given just a few years to live, but the scientist was to help open the Paralympics at the age of 70.
Despite spending most of his life in a wheelchair and able to speak only through a computer, the British theoretical physicist's quest for the secrets of the universe has made him arguably the most famous scientist in the world.
"I'm sure my disability has a bearing on why I'm well known," Hawking once said. "People are fascinated by the contrast between my very limited physical powers, and the vast nature of the universe I deal with."
Hawking was to make a rare public appearance in the Olympic Stadium to narrate the opening ceremony, giving star power to an event which brings the curtain up on the highest-profile festival of sport for the disabled in history.
His life's work has focused on the basic laws which govern the universe.
Much of his study has involved bringing together relativity (the nature of space and time) and quantum theory (how the smallest particles in the universe behave) to explain the creation of the universe and how it is governed.
In 1974, aged just 32, he became one of the youngest fellows of Britain's prestigious Royal Society.
Five years later he took the post of Lucasian Professor of Mathematics at Cambridge University, a post once held by Isaac Newton.
His fame moved beyond the world of academia in 1988 with the publication of his book A Brief History of Time, which explained the nature of the universe to non-scientists, and sold millions of copies.
Hawking's stardom was cemented in cameos in Star Trek and The Simpsons, where he tells the rotund Homer Simpson that he likes his theory of a "doughnut-shaped universe" so much that he might have to steal it.
Martin Rees, Britain's Astronomer Royal and a former president of the Royal Society, first met Hawking when they were both research students "and it was thought he might not live long enough to finish his PhD degree".
Rees said his survival made him a "medical marvel", but stressed that it was his work that would prove his lasting legacy.
"His fame should not overshadow his scientific contributions because even though most scientists are not as famous as he is, he has undoubtedly done more than anyone else since Einstein to improve our knowledge of gravity," he said.
Hawking was just 21 when he was diagnosed with amyotrophic lateral sclerosis (ALS), a form of motor neurone disease that attacks the nerves controlling voluntary movement.
Most ALS sufferers live for less than five years after diagnosis.
Hawking admitted he felt "somewhat of a tragic character" after his condition was diagnosed, but he soon returned to work, securing a fellowship at Cambridge, and married Jane Wilde, with whom he had three children.
There were fears for his health when he was forced to miss two events arranged to mark his 70th birthday in January, but he has bounced back.