Richard Griffiths is one of our finest and most distinctive actors. But what he's famous for is his huge girth, and for playing the predatory homosexual Uncle Monty in Withnail and I, and for abusing theatregoers who let their mobile phones ring during performances of The History Boys. He's stopped the show twice - once in London and once on Broadway - and when I learnt that I was to talk to Griffiths, the thought occurred that I should ask a friend to phone my mobile in the midst of our interview.
Fifteen minutes in and I rather wish I had. To be fair, Griffiths is suffering from jet lag: he flew into London right after the final New York performance of The History Boys and went straight to the royal premiere of the film of Alan Bennett's hit play. But my guess that he's always this cagey with journalists is confirmed when he admits to furious self-editing. "I'm never free when I'm in an interview," he says. His style is to speak very slowly as he takes longer and longer detours away from his personal life. A request for information about his wife, Heather (after all, there is a common assumption that Griffiths is gay), is met with a firm "no".
"Every time I've talked about my family in the past, people have ended up getting upset," he says. "So I said to my friends and family: 'I shan't refer to you at all, and there's nothing for you to get upset about. There's the deal.'" He finishes by flashing that chipmunk grin of his - a baring of teeth that could be seen as either jovial or aggressive. He won't even confirm whether or not he has any children (the cuttings suggest not). "I'm not interested in the casual interest of strangers," he says in his flat, trace-of-Teesside vowels. "I don't care about them and they don't care about me. I'm only here because of The History Boys."
Ah, yes, The History Boys. After sell-out runs in London (where Griffiths won an Olivier Award for his portrayal of Hector, the groping polymath of a grammar-school teacher), and on Broadway (where he won a Tony Award), Alan Bennett's unlikely hit has been turned into a film by the play's director, Nicholas Hytner, with most of the original cast, including Griffiths, Frances de la Tour and Stephen Campbell Moore. Tickets were sold out until the end of the play's run at the National Theatre, and were changing hands on eBay for prohibitive prices. If that seems extraordinary for a meditation on the meaning of school education, so is the fact that Bennett's play, about a group of grammar-school boys in early-1980s Sheffield trying to get a place at Oxford or Cambridge, should also sell out in New York.
"All the concerns in the play are current in America because, if anything, they have more of a problem with education-frenzy than we do," says Griffiths. "Mind you, some experienced money people said: 'It's a great show but it's got no context in New York. Pack for a fortnight and you won't be disappointed.'" Instead, the play was in New York for six months, and the run could have lasted another year, if it wasn't for American Equity rules governing British actors on Broadway. Griffiths has been away for the best part of a year, having also taken The History Boys to Hong Kong, Australia and New Zealand, where he picked up the carved walking stick he is using today. "I hurt my knee on the plane and it's become a friend. I'm slow anyway, and if you've got a stick, people are more patient with you."
Griffiths looks less bulky in the flesh than he does on screen, his still-considerable girth being the result of a childhood episode in which his pituitary gland was treated with radiation. "I went from being a beanpole - like a normal kid of the 1950s - and exploded. The weight piled on and didn't stop until into my adulthood. There's a three-year gap in my medical file. When I questioned it, they just said it had got lost. Later, I learnt that nobody's medical records has a lacuna in it extending more than a few weeks. Between the ages of seven, eight and nine... rien."
He was born in 1947 to deaf-mute parents in Stockton-on-Tees. His father was a steelworker. He has called his childhood "loathsome", and he describes his education as "a pathetic shambles". He attended a Catholic primary school, where he was beaten for missing Mass, and left secondary school at 15. "Where I grew up, Oxbridge is like the far side of the moon - even university was a cosmic notion."
After an unsatisfying stint at art school, Griffiths found his métier by way of a drama course at what is now Manchester Metropolitan University. He was spotted by Trevor Nunn in 1976 and spent the next 10 years at the RSC (he still lives near Stratford-upon-Avon), while clocking up various film and television appearances. His most cherished film role came in 1985 in Withnail and I. People still stop him in the street to quote Uncle Monty's most famous lines at him.
An unexpected side effect of this cult success was that Griffiths was assumed to be gay, and was forever being invited to be the head of various pink causes. "Unfortunately, I've done two screaming queens, Uncle Monty and Hector. There's 20 years between the two, but I've no doubt that someone is going to ask me to become the president of an Aids society or something."
For a younger generation, he is also the sinister Uncle Vernon in the Harry Potter movies, although boy-wizard fans should beware. "Some bloke came up to me in Tesco a couple of years ago at 11.30pm and said: 'Excuse me, would you mind telling my son here that you're Uncle Vernon?' I said: 'Get a grip. It's 11.30 at night - what's he doing out of bed? I'm not here to entertain people at this time of night.'"
This wasn't the last time a member of the public felt Griffiths's wrath. Yes, those mobile phones. "It's disrespect. I think there's a class of offence that the police should look at: disrespect," he says. "In America, four people - a family - each had a phone and each phone went off in response to different calls in the same five minutes. I said: 'Don't get me wrong. It's not me that's offended here. I get paid whatever happens. But you've shown the most incredible disrespect to a thousand people in this room.' At the Wyndham's, there was one woman, and her phone went off four times. And it turned out that she wouldn't turn off her phone because her husband was dangerously ill in hospital. So what was she doing at the show?"
Not everyone in the cast agreed with Griffiths's show-stopping interventions. "Frankie de la Tour's opinion is that you should just ignore it and carry on regardless. Personally, I would have them publicly garrotted. I would be a hanger and flogger if I was given my way." His hardline attitude extends to any youngster, it seems: "Everybody my age should be issued with a 2lb fresh salmon," he says. "If you see someone young, beautiful and happy, you should slap them as hard as you can with it. When they ask, 'Why did you do that?', you say, 'Because, you lucky young bastard, you don't know how fortunate you are.' And they don't..."
This comes out more wistful than bitter. If he genuinely feels youth is wasted on the young, he'll have plenty of time to discuss it with his next co-star: Harry Potter himself, Daniel Radcliffe. The two of them are to appear together on stage in Equus.
"Possibly... we'll see," he says, clamming up again. "For now, I'm getting back to my life. I haven't seen my home since January. It's been the most astonishing year because I've been having a marvellous adventure, and yet I kind of sympathise with people who have to live in exile, because I've so missed England."
'The History Boys' opens on Friday