Richard Griffiths can talk. Not chat, not polite conversation. This is raw, relentless talk. From the moment he walks through the door to the moment he leaves, he doesn't stop. I realise there isn't going to be a distinction between pleasantries before the interview and the actual on-the-record chat: I hit the record button on my dictaphone. And he stops, abruptly. "Oh... ah... where was I? Must have been the sight of a tape recorder."
Clad in a large navy-blue overcoat and an ill-fitting suit, which goes some way to hide his considerable girth, the 63-year-old actor launches into a variety of monologues, rants, anecdotes and digressions: "Robin Williams once said, up until the 20th century," begins one, seemingly from nowhere, "no woman could go to bed with a bloke without the possibility in the back of her mind that in nine months' time she would be dead." Er, sorry?
"Well, a guy that has sex has an excitement that lasts for a few minutes and it's done. Whereas the woman, because infant mortality at the end of the 20th century was massive, would suffer. My grandmother nearly died twice in delivery. She had about nine children ..." At times he steams ahead like a runaway train: I grope desperately for the brake.
He is often the sum of the many parts he has played throughout his rich and varied career: cantankerous Uncle Vernon in the Harry Potter series, camp and hammy Uncle Monty from Withnail and I and the thoughtful and principled Henry Crabbe in the 90s TV series Pie in the Sky.
Since the early 1980s Griffiths has been one of Britain's most prolific and treasured character actors. There have been supporting roles in Gandhi, Chariots of Fire, Sleepy Hollow, The History Boys and now the forthcoming instalment of the Pirates of the Caribbean franchise, where he'll portray a "very unfair" and "gross" version of King George II. Then there are the numerous TV roles: a mixture of the forgettable – Bergerac – to the acclaimed, such as Bleak House.
We meet in central London. He has driven the 100 miles from his home just outside Stratford-upon-Avon, which he shares with Heather, his wife of 30 years. Stratford may only be 150 miles from the North-east where he grew up, but for the actor it is a world away from the "ignorant, rough" North as he once called it.
Stratford is also the global home of Shakespeare and the Royal Shakespeare Company, where Griffiths started out. Unlike some of his RSC contemporaries he has never gloried in the coveted heroic roles: Hamlet and Romeo never beckoned; Falstaff and Henry VIII did.
In his latest role, in the comedy series Episodes, starting tomorrow, art imitates life as he portrays Julian Bullard, a Shakespeare veteran who soon falls foul of the phoney world of showbusiness casting and finds himself being replaced by the most non-English of actors in the form of former Friends cast member Matt LeBlanc.
Perhaps appropriately, the series also imitates his life. "Yeah, I was misled once," he says, with an unshakeable tang of his native Thornaby-on-Tees. "There was a movie, a pretty big Oscar-winning movie in the end [he won't say which one], and I was offered the 'third banana' in this picture. That's a Pete Postlethwaite phrase – lovely Pete Postlethwaite. It means you're not going to be Robert Redford or Penelope Cruz. You're going to be third on the list and that's a great place to be, especially at my age. I met the director in London and the star, who was Julia Roberts, who I adore. It was all set and they said: 'You're the guy'."
But he wasn't the guy: while working in the Lake District, he caught sight of a newspaper headline over someone's shoulder. It said: "Julia Roberts Cancels Movie". His movie. And it hurt. "I was gutted – beyond gutted. Then lo and behold, two years later it's remounted with a completely different cast and it won Oscars. I was gutted that no one replied to my phone calls when I went back for the part."
For someone who has switched seamlessly and succesfully from stage to television to film and back again, Griffiths appears, at times, remarkably jaundiced about the business to which he has devoted his life. "It's a very fraught situation in my business. [Episodes] is about the world of bullshit TV, and it's big money and big business.
"One of the big problems with TV and film is: what is good? Studios have no idea because they do not value artistic sensitivity and sensibility. What they value is income. They've always gone for that approach."
Despite Olivier and Tony awards for The History Boys, he is perpetually disappointed: "I'm miserable. I want nine Oscars and an entourage and arse-lickers all around," he says. There is irony, but only a hint. "I'm just a jobbing actor, which is OK but it's just hard. I'm happy with some of the work and some of the opportunities."
But he keeps going, battling for those coveted "third banana" roles. In truth, he's well equipped for the fight. He was born in 1947 in Thornaby-on-Tees in Stockton, and both his parents were profoundly deaf – his mother genetically, his father through an infection. The young Griffiths was picked on continually. "I was big and fat and had weird parents. I had a difficult time because my dad was physically a marvellous specimen, and he was fierce. And I wasn't, because I was too chubby. But I was expected to stand up for myself."
He recalls a time at school when he punched someone so hard it took the skin off his knuckles. His father reprimanded him: not for hitting, but for doing so without anything in his hands. He ran away from home frequently and, by his late teens, he was "getting good at violence", he says with a charming grin.
But standing up for himself wasn't working. He was always the one who incurred the wrath of disbelieving teachers, unable to accept that such a large, strong lad would be the victim rather than the perpetrator. Even now, anger can surface unchecked: he has famously bawled the audience out while on stage, incensed by their ringing mobile phones. In one case he ordered someone out of the auditorium after three offences.
He left school, aged 15, with no qualifications and started working at Littlewoods department store. He credits one of his bosses for giving him the impetus to go back to school with the warning that otherwise he'd never amount to anything.
He is scornful of the rough-and-tumble North-east, where the only acceptable art form was painting and drawing. "Everything else is raddled with 'pooferama' and deviancy. But if you can paint or sculpt – if it has craft in it and it's physical, it's OK," he says. "If you want to be into music, dance or acting, that's all disrespected." Nevertheless, he enjoyed painting and says when he went back to college to retake O-levels he was rather good at it.
Ironically, he chose drama O-level to get out of doing maths and kept it secret from his father. Qualifications allowed him to escape the North-east and study drama at the Manchester Polytechnic School of Drama. Graduation saw him working in small theatres both onstage and as a stage manager. Sir Trevor Nunn took him to Stratford and the RSC in 1975.
His escape from his background was complete: that same year he got his first film break in It Shouldn't Happen to a Vet. By the early 1980s he was landing supporting roles in big historical dramas such as Gandhi, Chariots of Fire and The French Lieutenant's Woman. But it was Withnail and I, produced on a shoestring in 1986, that anointed him one of Britain's great character actors, in the role of gay, predatory Uncle Monty.
The film went on to become a cult hit. People stop him in the street to quote Monty's most memorable line: "As a youth I used to weep in butchers' shops."
"They [the critics] just didn't get it," he fumes. "They trashed it, saying: 'Oh, it's just another boring, student film about some self-indulgent, toss-pot wasters."
He goes into another 10-minute rant about people "not getting" what the film was about, segueing to critics not getting Trainspotting first time around. In truth, one can't help feeling that, by now, he should be a little more content with his lot.
His latest film is Martin Scorsese's Hugo Cabret, about the early days of cinema in Paris. He's quick to heap praise on the director: "He's a marvellous bloke to be around. He's an absolute ball of energy. I'm exhausted just being around him. He's got this enormous personal grace and doesn't raise his temper. He's always looking for the positive in things."
And yet, when the time comes to have his photo taken, Griffiths first looks uncomfortable and then launches into another rant: "I hate having my photo taken. I hate all these posed shots – all that shit [mimics a vogue pose] about being important, trying to sell something ... the phoneyness of it all, that's why I've resisted it..."
But the phoneyness has its compensations. For a start there's his lovely blue coat: "Annie Leibovitz – I worked with her three times on a shoot... she gave me this coat." He points to the item in question. "She said: 'You look great in that, why don't you keep it?' This is only the third time..."
I turn my dictaphone off. But he carries on talking.
1947 Born 31 July in Thornaby-on-Tees, Cleveland. His father is a steelworker, his mother a shop worker. Both were profoundly deaf.
1962 Leaves school with no qualifications and starts work at the Littlewoods department store, but soon goes back to college, taking a drama O-level, among others.
1973 Meets Heather Gibson during a production of Lady Windermere's Fan. They marry in 1980.
1975 Gets first big TV and film break in the Five Minute Films and It Shouldn't Happen to a Vet.
1976 Is spotted by theatre director Trevor Nunn: 10 years at the Royal Shakespeare Company follow.
1982 Appears in Chariots of Fire and Gandhi a year later.
1987 Gains cult status as Uncle Monty in Withnail and I.
1994 Stars in Pie in the Sky, in role created for him.
2001 Appears in the first of the Harry Potter series as Uncle Vernon.
2004 Stars as Hector in Alan Bennett's The History Boys. Wins Olivier award and then a Tony award for the role on Broadway.
2008 Is appointed an OBE.
2011 Appears in the final instalment of the Harry Potter series, The Deathly Hallows: Part Two.
'Episodes' begins tomorrow at 10pm on BBC2