I am very proud of the letter I got back from Dr Hawking when I sent him a copy of my black velvet portrait of him:

He once said: “It would not be much of a universe if it wasn’t home to the people you love.”

For fellow scientists and loved ones, it was Hawking’s intuition and wicked sense of humour that marked him out as much as the fierce intellect that, coupled with his illness, came to symbolise the unbounded possibilities of the human mind.

“Stephen was far from being the archetypal unworldy or nerdish scientist. His personality remained amazingly unwarped by his frustrations,” said Lord Rees, the astronomer royal, who praised Hawking’s half century of work as an “inspiring crescendo of achievement.” He added: “Few, if any, of Einstein’s successors have done more to deepen our insights into gravity, space and time.”

The Canadian astronaut Chris Hadfield lamented on Twitter that “Genius is so fine and rare”, while the US rock band Foo Fighters was more succinct, calling Hawking a “fucking legend.”

Stephen’s deal with the Simpsons was that could use his image for free but he got to record his lines. He once called the show the “best thing on American television.”

Excellent obituary: Stephen Hawking, science’s brightest star, dies aged 76 | Science | The Guardian