Richard Griffiths: From poverty to Privet Drive, a life well lived

"And soon, I suppose, I shall be swept away by some vulgar little tumour." So Uncle Monty prophesied his own death in the film Withnail and I, before trying to bed a young Paul McGann – "I mean to have you, even if it must be burglary". Such are the caprices of stardom that, for 30 years afterwards, Richard Griffiths, who has died aged 65, would have these lines recited to him by fans in the street. "They quote stuff and expect me to know it," he said. "I find that very odd".

Stranger still is that an actor famous for his generous girth started life so skinny he had to receive medical attention. Aged eight, he was treated for a faulty pituitary gland. His metabolism slowed, and he gained 60 per cent of his body weight within a year. Having previously been picked on by bigger boys, Griffiths used his new size to his advantage, once beating up two boys who had thrown an apple at him. "It was the best fight I ever had," he recalled.

Richard Griffiths was born into "Dickensian" poverty to a steelworker father in North Yorkshire in 1947. For half his life, he was married to the actress Heather Gibson, who survives him. And yet, he is probably best-known for two roles in which he played a posh, predatory homosexual: Uncle Monty, and Hector, the motorbike-riding history master in Alan Bennett's 2004 stage hit, The History Boys (and in the film two years later, inset right). Sir Nicholas Hytner, who directed the play at the National, described Griffiths's performance as "quite overwhelming: a masterpiece of wit, delicacy, mischief and desolation, often simultaneously."

Indeed, so perfectly did he play these queeny older men, that many fans assumed he was gay. "Look, I'm just acting," he countered. By his own admission, Griffiths had a towering temper, which could explode at any moment. Griffiths said it came from his father, "a very aggressive man", who made extra money fighting in pubs. Younger audiences will remember him as Harry Potter's evil Uncle Vernon, though what Griffiths would have made of the BBC's headline on Friday, "Potter actor dies", one can only imagine.

He cut an avuncular figure in acting circles, mentoring younger talents such as James Corden and the comedian Jack Whitehall, who was his godson (his father, the agent Michael Whitehall, once represented Griffiths). "Sad news about Richard Griffiths," tweeted the younger Whitehall on Friday. "He was my godfather and friend. An amazing, funny and kind man, he will be much missed. RIP Riccardo." Corden, whose career was launched by The History Boys, recalled poker sessions and cocktail parties in Griffiths's dressing room. "He had the most brilliant sense of fun," said Corden. "He wanted to make sure we were enjoying what we were doing – that we knew how very special this moment was for us."

His own childhood was far from ideal: three of his four siblings died, two were stillborn, and a sister died days after birth. His parents were both deaf and the family communicated by sign-language; there was no television or radio. Venturing from this tough background into acting was a giant leap, which he determined to take, aged 17, after seeing a spellbinding production of Edward Albee's Who's Afraid of Virginia Woolf?. He kept secret his application to do a drama course at the Northern College of Music, and his father "raged at its pooffery" when he found out Griffiths was to become an actor.

After some years of struggle, his talent was spotted by Trevor Nunn, then artistic director of the Royal Shakespeare Company, and Griffiths moved to Stratford and spent years working through the canon of Shakespeare roles, from Henry VIII to Bottom. Inevitably, he used his size to his advantage, though he didn't rely on it for comic effect. His enunciation and facial expressions could be devastatingly funny. But it was his heart that would finally give way, and he died of complications during an operation on Friday morning.

Interviewed by this newspaper in 2011, he was a generous fund of anecdotes, and spoke candidly about his difficult upbringing. Despite his fame, he was modest and kind. "In his gregarious way, he didn't stop talking for the whole hour we spent together – even through his photo-shoot," recalls the journalist, Paul Bignell. "I couldn't help think it might be a technique to stop journalists asking probing questions. But he gave great interview copy. Despite his own admission of a fiery temper, I saw none of it that day, rather a humble man who, despite the plaudits and fame, said he was still 'just a jobbing actor'."

As both Hector and Uncle Monty, Griffiths cut an ultimately tragic figure, that of a fat, lonely, gay man, enraged by badly behaved cats. "Oh my boys, my boys," went one typical speech. "We're the end of an age, we live in a land of weather forecasts and breakfasts that set in. Shat on by Tories, shovelled up by Labour. And here we are, we three – perhaps the last island of beauty in the world."

For all his bonhomie, Griffiths could reduce audiences and colleagues to tears. Corden recalls the last performance of The History Boys on Broadway, in which Griffiths's character dies in a motorbike accident, and reappears as a ghost. "We were all so sad because it was our final show that many of us were crying before we reached the interval," says Corden. "I always presumed Richard – being such an old pro – wouldn't get caught up in the moment like that. But when he came out to deliver his final lines he was as moved as the rest of us. In the role of Hector, he had shown the world he was so much more than a brilliant scene stealer. He could be, if the part was right, a leading man."