Rik Mayall was happy and healthy in the hours before his death, according to his Comic Strip Presents colleague Peter Richardson, whose son was one of the last people to see the actor alive.
Peter, who directed Rik in a series of TV shows, said the 56-year-old was 'such a star'.
He told the BBC Radio 4 Today programme that his son saw him around half an hour before he died at his London home.
He said: "He was happily chatting away and it was very quick and we still don't quite know what happened, but it was a seizure of some sort."
Rik, who leaves his wife, Barbara, and three children, Rosie, Sidney and Bonnie, survived an almost fatal quad bike accident in 1998 which left him in a coma for several days.
Peter said: "He had 16 years after the quad bike and at the time I don't think people thought he would survive that but he lived for another 16 years and it was just shocking that he went - he was so happy and seemed very healthy when he did go."
Rik shot to fame playing poetry-writing anarchist Rick in The Young Ones, and enjoyed a glittering career which saw him appear in Britain's best-loved shows including Blackadder and Bottom.
Peter said the star 'loved playing the bad boy', but was very different in real life.
He said: "He always wanted to be a rebel, but in fact was a lovely family man who did the washing up and was just a very warm person and not as selfish and vain as he liked to make out really."
Close friend and long-time collaborator Adrian Edmondson led the tributes to Rik, saying he felt privileged to have shared 'carefree stupid days' with him at Manchester University, where the pair studied.
He said: "There were times when Rik and I were writing together when we almost died laughing. They were some of the most carefree stupid days I ever had, and I feel privileged to have shared them with him. And now he's died for real. Without me. Selfish b*****d."
Stephen Fry, who also starred in Blackadder, said on Twitter: "Simply distraught to hear of the death of Rik Mayall. An authentic comedy genius and a prince among men."
It is not yet confirmed what caused Mayall's unexpected death and his wife Barbara Robbin - who is understood to have found his body at their home in Barnes, south west London - told the Daily Mirror she had no idea what had caused his death and would have to wait for a coroner's report.
A Scotland Yard spokesman said officers were called by London Ambulance Service to a house in Barnes where 'a man, aged in his 50s, was pronounced dead at the scene'.
He added that the death was not believed to be suspicious.
Rik was born in Harlow, Essex, to drama teacher parents and launched his comedy career on stage in a duo, The Dangerous Brothers, with Ade Edmondson.
