John Sessions had the unusual distinction of not only providing the voices of Norman Tebbit, Peter O’Toole and Sir Laurence Olivier for the 1980s television satire Spitting Image, but also being featured as one of the show’s puppets. “They did John Sessions going up his own arse,” recalled the actor-comedian, who wrote poetry at age eight and could recite Finnegans Wake verbatim.

This affable brainbox, whose talent for mimicry and improvisation made him a fixture on panel shows such as Have I Got News for You and QI, admitted that his love of history made him a “bit punchable”, adding: “I’m able to think quickly with facts.” The actor Timothy Spall once said that Sessions “could come across as a bit of a clever dick”, something that Sessions blamed on not having been to Oxbridge. “I can’t even belong to the club of comedians who went to Cambridge,” moaned the entertainer, who almost completed a PhD.

Despite such introspection Sessions enjoyed an eclectic career, ranging from one-man routines to stagings of Chekhov. His impressions were also at the heart of Stella Street (1997), a spoof soap opera about stars such as Keith Richards, Michael Caine and Al Pacino who live on the same suburban road with a corner shop. He told Radio Scotland that he had once met Richards and the other Rolling Stones, adding: “Keith said he really enjoys it and he’s thinking of getting a little corner shop.”

On television he was Zipser, the sexually inexperienced student in Channel 4’s adaptation of Porterhouse Blue (1987), he teamed up with Robbie Coltrane for Boswell & Johnson’s Tour of the Western Isles (1993), and in last year’s Victoria he played Lord John Russell. On the big screen he was seen with Mel Gibson and Anthony Hopkins in The Bounty (1984), as Harold Wilson in Made in Dagenham (2010), and, crossing the floor, as Edward Heath alongside Meryl Streep’s Margaret Thatcher in The Iron Lady (2011). His soft Scottish burr meant he had a busy sideline in audiobooks, while on shows such as Whose Line Is It Anyway?, where he often appeared with his friend Stephen Fry, he could improvise visiting the dentist in the manner of Ernest Hemingway or James Joyce.

“I can’t even belong to the club of comedians who went to Cambridge,” moaned Sessions.

Although Sessions’s star shone bright in the late Eighties, especially with his one-man show The Life of Napoleon that played at the Albery Theatre from 1987 to 1988, he tended to fall between two stools: actors saw him as a comedian; comedians thought he was an actor. He also never shook off his impostor syndrome, dreading what the critics would say and fearing being found out. He spoke of envying Timothy West’s passion for steam trains, Michael Gambon’s dexterousness with a lathe and Dulcie Gray’s knowledge of butterflies, adding: “If I had a hobby, perhaps I would get everything in proportion.”

Sessions played James Boswell to Robbie Coltrane’s Samuel Johnson and Leo Sho-Silva’s Joseph in the BBC comedy series Boswell & Johnson’s Tour of the Western Isles.

John Gibb Marshall was born in Largs, on the Clyde coast of Ayrshire, in 1953, the son of John Marshall, a Protestant gas engineer, and his Catholic wife, Esmé (née Richardson), who worked in a bookshop and had a reverence for books that she passed to her son. He described his father as “very wise, but also chauvinist, anti-Semitic and racist”. One of his favorite childhood memories was sailing around the island of Ailsa Craig on the Duchess of Montrose, although his heart was broken when the excursion steamer was scrapped in 1964.

He had a twin sister, Maggie, who became a lawyer in Canada, and an older brother, Bill, who joined the navy when John and Maggie were four. “We had a big map on the wall with a little magnet tracking his ship,” Sessions recalled. “When he was home on leave, he would play me records and take me to concerts. I got my love of classical music from him.”

Their father’s work took the family to the home counties when John was three and he attended Bedford Modern, an “idyllic public school”. The scripture teacher, an ebullient ex-fighter pilot, encouraged him to improvise Bible stories. Later he was bullied at St Albans Grammar School, but nevertheless acquired a taste for Shakespeare after studying The Tempest for A-level. During one holiday he and a friend washed dishes in a Lyons tea shop, using the proceeds to spend a couple of weeks in Mallorca. He then read English literature at University College of North Wales, in Bangor, where he appeared in comedy shows with titles such as Look Back in Bangor and Marshall Arts.

Taking himself to Canada he started a PhD on John Cowper Powys, the British philosopher, at McMaster University in Hamilton, Ontario. “I was there for four years, but didn’t stay and didn’t complete it,” he said, confessing that “I was doing plays and one-man shows at the same time”. He later described his dissertation as “200 pages of rubbish”.

Back in Britain in the late 1970s he was offered a place at the Royal Academy of Dramatic Art, despite turning up for his audition with a hangover. He earned his keep by teaching English to Japanese businessmen. There he met Kenneth Branagh and later appeared in Branagh’s Shakespearean films Henry V (1989) and In the Bleak Midwinter (1995) while also finding his way on to the comedy circuit. “My plan was to do two careers at once — to be a comedian and to be an actor,” he explained. The name John Sessions came about because there was another John Marshall in Equity.

Sessions had a habit of batting away questions about his private life. However, his homosexuality was revealed in 1994 while he was appearing at the Royal Court in My Night With Reg, a comedy about gay life in London: “I was interviewed by the London Evening Standard and asked very robustly, ‘Are you gay?’ I said, ‘Yes I am, but my parents don’t know’. The journalist said she thought I should tell them and outed me.” His mother, with whom he had tried as a teenager to discuss his sexuality but quickly backtracked when he saw her look of horror, died unexpectedly six weeks later.

In the late 1970s he was offered a place at the Royal Academy of Dramatic Art, despite turning up for his audition with a hangover.

During the same show he suffered stage fright. “I just got frightened. Then I got frightened of being frightened. I was thinking, ‘What if I’m on stage and suddenly panic and can’t remember my lines?’ To let that go on was stupid. I should have gone back straightaway. I kept tormenting myself with the fear of the words not coming out, or forgetting lines.” He avoided live theater until 2013 when the novelist William Boyd persuaded him back with his play Longing, based on two Chekhov stories.

Last year Sessions portrayed Lord John Russell in the British TV series Victoria.

On one occasion Sessions was playing opposite Rosanna Arquette in the Hollywood film Sweet Revenge (1990), but was terrified at getting so close to a woman. He recalled how Arquette employed the help of strategically applied marmalade to relax him, before eventually losing patience and saying: “For Christ’s sake stick your tongue down my throat.”

Sessions, who lived in Wimbledon, southwest London, was not domesticated. “When I’m going out in the evening and haven’t had time to iron a shirt, I buy a new one on my way home,” he said. “I’m always going out with a line across my stomach from the box.” He was also deeply impractical. “I could no more put up a shelf than compose Beethoven’s Ninth,” he added. He struggled to write without a freshly lit Silk Cut cigarette to hand, but kept his figure by lifting weights four times a week. During darker moods he was prone to heavy drinking.

His political views lay to the right. Critics called him a “plastic Scot” because of his disdain for the Holyrood parliament (“Och, it’s just nonsense … a waste of money”) and his opposition to Scottish independence (“absolutely ridiculous”). Having championed Labour in the 1990s he migrated to Ukip and supported Britain’s withdrawal from the European Union, saying: “The United States of Europe is madness.”

Gray-haired and often wearing large glasses, he was described as looking like Ronnie Barker “or a retired colonel you might run into at a golf club in Surrey”. It was an image he seemingly rejoiced in, telephoning the BBC to object to the misuse of words on the airwaves. “I’m sick to the back teeth of hearing people say ‘mitigate against’; ‘militate’ is the verb,” he harrumphed. As if to emphasize the point he appeared in Pudsey the Dog: the Movie (2014) playing Basil Thorne, an old buffer who tried to eviscerate both Pudsey, the dancing canine that won Britain’s Got Talent in 2012, and an idyllic village that he believed would benefit from a shopping mall.

The melancholic moods remained a constant. In 2014, while grieving the deaths of actor friends such as Richard Briers, Richard Griffiths and Bob Hoskins, Sessions was appearing in a one-man show about Harry Lauder that dealt with the Scottish singer’s heartbreak over the death of his son in the First World War.

“I feel ancient,” he told The Scotsman. “Time is running out. You have to do things. I need to do things. I need to travel more.”

John Sessions, actor, was born on January 11, 1953. He died from a heart attack on November 2, 2020, aged 67