Stephen Fry has led the tributes to "lovable and loving" actor and comedian John Sessions, who has died aged 67.
Sessions was best known as a panellist on 1980s and 90s improvisation TV/radio 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.
Fry described him as "warm, vulnerable, lovable and loving as anyone can be", with "so, so much talent".
The actor, comedian and author wrote on Twitter: "He could make me laugh until I was sick and dizzy with pleasure and exhaustion."
I’m already missing Johnny Sessions dreadfully. As warm, vulnerable, lovable and loving as anyone can be. And so so much talent. He could make me laugh until I was sick and dizzy with pleasure and exhaustion. I can’t bear that he’s gone.— Stephen Fry (@stephenfry) November 3, 2020
Other comedians also paid tribute. 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."
Devastated by the loss of my great friend and legend Johnny Sessions. He was a genius— Ronni Ancona (@RonniAncona) November 3, 2020
RIP John Sessions - such an original force of clever wit and talent - the best smile - a port in a storm to all— Helen Lederer (@HelenLederer) November 3, 2020
Jeez. Another one. John Sessions. Just the best, he’d blow everyone away on Whose Line with his speed of thought & breadth of reference. Utterly absorbed by Hollywood, its characters and stories, brilliant raconteur, genius mimic. A flash of brilliance just went out.— Rory Bremner (@rorybremner) November 3, 2020
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."
His friend Ian Hislop, Private Eye editor, said Sessions was a "very modest man" and would have been flattered by all the attention.
"I was delighted to see him described as a star. He probably thought he wasn't but he was. And he was quite the funniest man, in real life, that you could ever meet," he told the BBC.
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."
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 Grant and broadcasters Mariella Frostrup and Samira Ahmed were among the others paying tribute.
Bobby Ball and now John Sessions! Two very different performers who both absolutely inspired and delighted me at different times. Lovely, funny men.— Robert Webb (@arobertwebb) November 3, 2020
John Sessions, in various forms, has made me laugh my arse off for 30 years. I was delighted to lure him into to joining us on Moone Boy for a short while and he was glorious. The world may move a little slower today, without his dynamo of a mind to propel it. Thank you John. https://t.co/BkqP1CjBod— chris o'dowd (@BigBoyler) November 3, 2020
I’m so sorry to hear that my old friend John Sessions has died. I knew him in graduate school in Canada in the 70s where, under his real name John Marshall he satirised the faculty so accurately we laughed till our bones hurt.— Linda Grant (@lindasgrant) November 3, 2020
So sad to hear of the death of #johnsessions A great actor and an interesting man who I always enjoyed encountering.— Mariella Frostrup (@mariellaf1) November 3, 2020
Should add I will always remember John Sessions giving our the medals at my daughter primary school sports day. He had a lovely smile and seemed so chill. I just thought of all the wonderful work he’d done by then and how much joy he’d given me.— Samira Ahmed (@SamiraAhmedUK) November 3, 2020