Stephen Hawking missed his own 70th birthday party yesterday at Cambridge University on doctor's advice - he was recovering at home from an infection that had put him in hospital for a few days last week.
The world's most famous living scientist, who was diagnosed with motor neurone disease in 1963 at the age of 21 and given just two years to live, nevertheless used a prerecorded speech to deliver his birthday lecture.
The packed auditorium included the Astronomer Royal, Sir Martin Rees, Professor Saul Perlmutter, the Nobel Prize winner in physics last year, businessman Sir Richard Branson and model and former Cambridge arts student Lily Cole.
In a highly personal talk, Hawking spoke movingly of the role his father played in picking him up from the devastating diagnosis when he was just beginning his PhD at Cambridge University - and how his doctor dropped him as a hopeless case and then never saw him again.
"My mother realised something was wrong and took me to the doctor," Hawking said. "I spent weeks in Bart's Hospital [in London] and had many tests. They never actually told me what was wrong, but I guessed enough to know it was pretty bad, so I didn't want to ask.