Actor and comedian John Sessions has died at the age of 67.
He was best known as a panellist on 1980s and 90s improvisation TV show Whose Line Is It Anyway?, and for Stella Street, Spitting Image and QI.
His acting credits included TV dramas Porterhouse Blue and Victoria, and Kenneth Branagh's 1989 film of Henry V.
Comedian Ronni Ancona described him as "a genius", while Helen Lederer remembered him as "such an original force of clever wit and talent".
Rory Bremner said Sessions was "just the best, he'd blow everyone away on Whose Line with his speed of thought & breadth of reference". He added: "A flash of brilliance just went out."
The Ayrshire-born star died from a heart condition, his agent said.
During his career, he provided voices on Spitting Image in the 1980s - the only person to both provide impressions and be featured as a puppet on the satirical show.
The programme was among the trailblazers of alternative comedy, he told BBC Radio Scotland in September. "You really felt you were at the cutting edge of comedy," he said.
His impressions were also at the heart of Stella Street, a spoof soap opera about megastars like Keith Richards, Joe Pesci and Roger Moore who lived on the same suburban road, which launched in 1997.
Sessions recalled meeting Richards and the other members of the Rolling Stones. "They watched the show," he told Radio Scotland. "Keith said he really enjoys it and he's thinking of getting a little corner shop."
Paying tribute, comedian Sanjeev Bhaskar saidSessions was "always warm and fun company and amazing improv ability".
Meera Syal remembered himbeing "always the funniest and kindest man in the room", while Jack Dee described him as "a delightful, funny, generous and hugely gifted man" and Sally Phillips said he was "unpredictable, dangerous, adorable".
Sessions appeared on the first ever episode of QI, and the team behind the panel show said: "His incredible wit and encyclopaedic knowledge played a huge part in the show's history and everyone at QI is deeply saddened to learn of his passing."
Broadcaster Danny Baker remembered him as "terrific company always and a true talent", and Michael Spicer described him as "a character actor with such extraordinary range and so very, very funny".
Sessions was born John Marshall in Largs, Scotland, in 1953, and moved to Bedfordshire with his family when he was three.
He was accepted by Rada at the age of 26 in 1979. Eight years later, his one-man theatre show The Life of Napoleon transferred to the West End. "He is like nobody else," The Times' critic wrote. "He uses language like a poet; he can jump from the raft at Tilsit to Huck Finn on the Mississippi and make the metaphor work."
Soon after, Sessions made his acting breakthrough on screen in Channel 4's Porterhouse Blue, before showing his surreal and cerebral comic energy on Whose Line Is It Anyway?
"When I left Rada, my plan was to try and do two careers at once - to be a comedian and an actor," he told The Guardian in 2014. "For some years, I managed to juggle the two, but I never felt I joined either club."
He went on to star in a string of his own BBC TV shows, such as a self-titled solo improvisation series in the late 1980s, followed by John Sessions's Tall Tales and John Sessions's Likely Stories.
But he never quite achieved the stardom of his friends Branagh and Stephen Fry. He said he "ran out of steam" when he turned 40. "As I was getting older, I wasn't getting more confident, I was getting less confident," he told The Guardian. "I lost my way."
His other TV credits included Victoria, The Loch, Just William, Tom Jones, and Gormenghast; and he had film roles in The Good Shepherd, The Merchant of Venice and The Bounty.
His knack for impersonating politicians was put to use in dramas too - playing former prime minister Edward Heath in the 2011 film The Iron Lady; another ex-premier, Harold Wilson, in 2010's Made in Dagenham; and former chancellor Geoffrey Howe in the 2009 Thatcher biopic Margaret.
But he told The Telegraph in 2013: "I don't think I was very good at managing my career. You need to carve your own path and not just bob along."
Recently, he had narrated a 10-part radio adaptation of children's book series The Adventures of Captain Bobo.
In a statement, his agent Alex Irwin said: "It is with great sadness we can confirm that on Monday 2nd November, the actor John Sessions died at his home in South London. He will be hugely missed."
Peep Show star Robert Webb, actor Chris O'Dowd, author Linda Grantand broadcasters Mariella Frostrup and Samira Ahmed were among the others paying tribute
