Friday Night Dinner star Paul Ritter has died of a brain tumour at the age of 54.
The actor, who also starred in Harry Potter And The Half-Blood Prince, the acclaimed TV series Chernobyl and the James Bond film Quantum Of Solace, died at home with his family by his side.
His agent said: "It is with great sadness we can confirm that Paul Ritter passed away last night… peacefully at home with his wife Polly and sons Frank and Noah by his side.
"He was 54 and had been suffering from a brain tumour.
"Paul was an exceptionally talented actor playing an enormous variety of roles on stage and screen with extraordinary skill.
"He was fiercely intelligent, kind and very funny.
"We will miss him greatly."
Comedian Rob Delaney was one of many who posted Twitter tributes, describing Ritter as "unreal talent".
"Knocked it out of the PARK in Chernobyl. Watching it I consciously thought, ‘Oh, we have a new movie star’," he wrote.
"Between that and how funny he was in Friday Night Dinner… just unreal talent. Rest in peace, Paul Ritter."
Friday Night Dinner writer Robert Popper said Ritter was "the greatest actor I ever worked with".
Actor Mark Gatiss said he was "saddened" to hear of Ritter’s death.
"Paul Ritter. What an actor. What a presence. So shocked and saddened by this awful news. RIP," he wrote on Twitter.
Russell Tovey said Ritter was "one of the nicest and best actors you’ll ever meet".
"I had the absolute pleasure of a first play at 19 with him, he called me a ‘plonker’ when I left him hanging on stage once at a missed entrance cue – I’ve never forgotten it and never did it again – RIP mate x," tweeted the actor.
Actor Stephen Mangan wrote: "Trying to find a way to talk about Paul Ritter and struggling. My friend since we were students together.
"So much talent and it shone from him even as a teenager.
"I was so lucky to know him and lucky too to work with him many times over the years. Wonderful man. RIP."
In Channel 4’s Friday Night Dinner, Ritter played the quietly-suffering, often shirtless, hard-of-hearing husband and dad Martin Goodman.
His widely-acclaimed role as Anatoly Dyatlov, the deputy chief engineer at the nuclear power plant in Chernobyl, led to the five-part miniseries becoming the best-rated show ever on global movie and TV website IMDb – and hailed as "the greatest drama of all time".
In Harry Potter And The Half-Blood Prince, he played wizard Eldred Worple.
Other notable roles were as Guy Haines in James Bond film Quantum Of Solace, in period drama Belgravia, as Billy Cartwright in Vera and Sir John Seymour in Wolf Hall.
Born in 1966, Ritter made his TV debut in an episode of The Bill in 1992 and became an acclaimed stage actor, working with the National Theatre in The Royal Hunt Of The Sun, All My Sons, Coram Boy, The Hot-House, The Curious Incident Of The Dog In The Night-Time and as John Major in The Audience opposite Dame Helen Mirren as the Queen.
He also worked with the Royal Shakespeare Company and played Pistol in the 2012 mini-series The Hollow Crown.
Ritter was nominated for a Tony Award and an Olivier for his role as Reg in the Old Vic’s revival of The Norman Conquests.
Hugh Adams, of charity Brain Tumour Research, said: "Our deepest condolences go to Paul’s family and friends following the devastating news that he has died from this terrible disease.
"Approximately 16,000 people each year are diagnosed with a brain tumour and unlike most other cancers, incidences of and deaths from brain tumours are rising.
"Just 12% of those diagnosed with a brain tumour survive beyond five years compared with an average of 50% across all cancers.
"We are proud to be building a network of experts in sustainable research at dedicated centres of excellence whilst influencing the government and larger cancer charities to invest more nationally, getting us closer to finding a cure."
Ritter is due to appear in the Friday Night Dinner 10th anniversary episode, which will air on Channel 4 later this year.