When he was diagnosed with Motor Neurone disease at the age of 21, doctors thought he would not live more than another few years. But this Sunday Stephen Hawking turns 70 and is celebrating a life of outstanding achievement.

Dr Harvey Reall, a reader in theoretical physics at Cambridge and a former student of Professor Hawking, recalls his many conversations with Stephen Hawking as involving a fair amount of "banter". Humour, he says, is something that is very important to the scientist.

Professor Hawking's biographer Kitty Ferguson says that family has meant a tremendous amount to him. Physics "is not all his life", she adds - there is much more to him than just the science.

On the issue of science though, she says that Stephen Hawking takes ordinary people on a "huge adventure", giving people a sense of wonder when they follow him.

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