Actor and comedian John Sessions has died aged 67, his agent has confirmed.
Born in Ayrshire, Scotland, he attended the prestigious drama school RADA in the late 1970s and went on to an accomplished career in film and television.
He was well known for his improvisational comedy skills, entertaining fans across the first three series of sketch show Whose Line Is It Anyway?.
He went on to perform as various characters on the satirical comedy series Spitting Image, where his extensive literary knowledge became a great asset.
Sessions reunited with his Whose Line collaborator Stephen Fry when he became a regular panellist on BBC Two's popular series QI, appearing in a total of 10 episodes.
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The programme's official Twitter account has paid tribute to him today, saying his "incredible wit and encyclopaedic knowledge played a huge part in the show's history".
In more recent years, Sessions has appeared in a number of prolific films, working with Meryl Streep on Margaret Thatcher biopic The Iron Lady and comedy drama Florence Foster Jenkins.
He also starred opposite Tom Hardy in Kray Twins drama Legend, and Sir Ian McKellen in 2015's Mr Holmes, where he played the famous detective's brother, Mycroft.
Doctor Who fans will remember Sessions from his roles in animated adventure Death Comes To Time and his voice role in 2014's Mummy On The Orient Express, starring Peter Capaldi and Jenna Coleman.
Audio drama producers Big Finish are among the many to have paid tribute to him since the news broke.
Sessions is a recognisable face across the broad landscape of British film and television, appearing in teen drama Skins, BBC sitcom Outnumbered, and Benedict Cumberbatch's Sherlock.
His peers in the world of entertainment have begun sharing their condolences about his passing, including Peep Show star Robert Webb, who says that Sessions's work "inspired and delighted" him.
Comedian Rufus Hound called attention to his recent performance in We're Doomed, which told the story of how iconic sitcom Dad's Army made it to the screen.
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