Comedy writer David Nobbs has died, the British Humanist Association (BHA) said.
The 80-year-old was best known for writing the classic 1970s British sitcom The Fall And Rise Of Reginald Perrin.
BHA chief executive Andrew Copson said: "David Nobbs was a very special talent and we were all honoured to have worked with him over his years as a patron of the BHA."
Comedian John Cleese also paid tribute to Nobbs.
He wrote: "Very sad today to hear of the death of David Nobbs. First worked with him on the Frost Report in 1966... a lovely kind, gentle man with a delicious sense of humour.
"He wrote many top-class shows and books. His masterwork: the Reggie Perrin shows."
More tributes flooded in from the world of comedy.
The Office creator Ricky Gervais, borrowing a catchphrase from Perrin's tyrannical boss CJ, said: "I didn't get where I am today by not knowing what a genius David Nobbs was. RIP."
Little Britain starMatt Lucas wrote: "Reggie Perrin and A Bit Of A Do were masterpieces. David Nobbs leaves the world a richer place."
Irvine Welsh, who wrote the novel Trainspotting that was made into a hit film, posted on social media: "Very sad to hear of the death of inspirational David Nobbs, who I had quite a few laughs with.
"A comic genius and an excellent human being."