Evolutionary biologist Richard Dawkins and retired Doctor Who actress Lalla Ward have paid tribute to the life of their close friend, the author Douglas Adams, on what would have been his 62nd birthday.

Professor Dawkins and Ms Ward, who married six months after they were introduced to each other at one of Mr Adams’ parties, shared stories and secrets about the Hitchhiker’s Guide to the Galaxy author at Highgate Cemetery in Swain’s Lane on Tuesday.

Mr Adams died suddenly at his Californian home in 2001 from a heart attack at the age of 49 and is buried in Highgate Cemetery East.

At one glittering dinner party for Mr Adams’s 42nd birthday – where guests included Pink Floyd, Stephen Fry and members of Monty Python – the author’s 200 guests had to work out where they were sitting by reading place cards that only revealed who was sitting to the left or to the right.

“Each card had on it a small question to do away with small talk,” said Ms Ward, who played Doctor Who companion Romana alongside Tom Baker from 1979 until 1981.

Mr Dawkins, the atheist author of The God Delusion, added: “My card read: the person sitting to the left is Richard Dawkins. Why don’t you ask him to say grace?”

Mr Adams first met Ms Ward in 1978, when he was commissioned to write an episode of Doctor Who.

On the strength of that episode, he was quickly made script editor of the show for season 17. But it was not until the late 80s that Mr Dawkins became friends with him.

“He loved science,” the 72-year-old biologist said. “He had read one of my books and said it had killed whatever was left of his religious faith. I’m very proud of that. He was my first and only convert.”

Mr Dawkins told the audience of about 30 people that Mr Adams’s literary agent, Ed Victor, once locked him up in his hotel room for three weeks until he finished the fourth book in the six-part Hitchhiker series, So Long and Thanks for All the Fish, allowing him out to Hyde Park occasionally.

“We went to visit his grave before this,” Ms Ward, 62, said. “It was unbelievably moving walking around Highgate Cemetery and seeing the little pot of pens there instead of flowers. I dropped a pen in it.

“I feel that someone who had as big a personality as he did doesn’t really go away.

“He didn’t believe in an afterlife, but you know in cartoons when Bugs Bunny crashes through a wall and makes a big impression? That’s how I feel about Douglas.

“God, how we miss him.”