The PR office in Soho where I meet Timothy Spall is all shiny surfaces and self-importance. Spall is magnificently incongruous here, his dishwater-blonde hair swept over into a raffish curve. He is wearing a pinstripe suit and waistcoat complete with pocket watch on a chain.
He could almost be a fictional invention - people often describe him as Dickensian. But to my mind, with his barrel stature, uneven features and beaver moustache, he's more like a character in The Wind in the Willows.
He has clever, expressive hands and long fingernails. His hands are an important part of his tool kit as an actor, and an accessory to his extraordinary performance as the artist JMW Turner in a new biopic from director Mike Leigh, which won him the best actor award this year at Cannes. In the scenes in which he paints, they look convincingly capable of producing works of genius.
Spall is pretty good with a paintbrush himself. In preparation for the role, he spent two years studying to paint like Turner under the renowned art teacher Tim Wright, and recovered an aptitude that had been buried for decades. At school at an inner-city comprehensive, he failed all his A-levels except art, for which he got an A. He takes out his phone to show me a picture of a reproduction he painted, "a full-scale oil" of Snow Storm - Steam Boat Off A Harbour's Mouth which is startlingly good. "I look at it in the morning and think, how the f**k did I do that?" he says, his voice a silty, estuary growl.
Even by the standards of the Mike Leigh method, his degree of immersion in the role borders on the obsessive. Like Turner, Spall is a self-taught man. He is driven by a hungry curiosity and as an actor, is scholarly as well as visceral - as if he's in it for the education as much as anything else.
He can hold forth with knowledge and eloquence about Turner's world, the Enlightenment values and ideas he absorbed, the social, historical and personal details he used as the building blocks of his rendition of the artist's internal life. I get the impression that when talking to Spall, it must often feel like there aren't enough hours in the day.
Three times during the making of the film, he went to visit the artist's grave. "He's buried in the crypt of St Paul's Cathedral," he says. "Which is just down the road from where I live." He went once "before we started - I apologised in advance. Once in the middle of it, and said 'I hope you're not taking offence', and the last time I went and I just knelt on his grave. I pretended I was doing my shoelaces up. And I was so tired and emotional, I just dropped a tear on it. And then wiped it off with the sleeve of my coat, and said 'I really hope I've done you right, I really do.'" His Turner is beauty and beast rolled into one - an uncanny mix of soaring finesse and brutishness. He trundles through the Royal Academy like a hedgehog stuffed into a tail-coat; grunting, spitting and bristling.
"This implosive thing that he's got," Spall explains, "people often talk about the grunting and that, and that's the kind of manifestation of somebody who has got a billion things to say but just doesn't want to express them, and is not going to because it's too complex. So he brings it down into himself. And that's all about turning everything back into this engine that drives this genius that comes out the end of his arm."
Part of his ability to understand Turner comes from the parallels between them. Both are working-class Londoners. Spall's mother was a hairdresser, Turner's father a barber. Both are self-taught. Growing up in Battersea, Spall flunked school but developed an interest in classical music and art, spending his time wandering around the Tate. A teacher spotted his talent for acting and suggested he auditioned for Rada, where he was later named the most promising actor in his year.
Now 57, his win at Cannes is the cumulation of decades of notable character work. He's collaborated with Mike Leigh six times, was made famous by Auf Weidersehen, Pet, played Winston Churchill in The King's Speech and Peter Pettigrew in the Harry Potter series. He seems to be cautiously enjoying his moment of glory. "If people like it, it's great," he says, while a bad review "is like being kicked in the gonads".
The recognition is made all the sweeter for the fact that he feels lucky to still be around at all. In 1996, Spall was diagnosed with acute myeloid leukaemia and nearly died. He was supposed to be at Cannes with the rest of the cast of Secrets and Lies celebrating winning the Palme D'Or, but while they were on stage, he was having chemotherapy instead.
Shane, his wife of more than 30 years ("we're joined at the hip"), recently published her diaries of that time in her book The Voyages of the Princess Matilda. They are a moving read - a document of devotion written as her husband appears to almost slip away in front of her. "It was difficult when I read it," he says. "She was there for me. But... didn't tell me what she was feeling, and I didn't tell her a lot of the time what I was feeling." Still, he knew. He and Shane have three kids, and watching his family suffering was the only part of the ordeal that was "unbearable" he says. "Being ill is being ill, you just get on with it. But what happens to other people when you are ill is a problem," he says. "When I read (her diaries) it just qualified how difficult it was. And it also made me realise I was bloody glad I survived."
It was touch and go for a while, but eventually he started to make slow but steady progress back to health. "When I was ill, I said to my wife ... 'if and when, I don't die we're going to get a Rolls Royce and a boat. She said 'Alright.' She wasn't going to argue with a dying man." The boat played a big part in his recovery. "Reading Dickens and narrow-boating," he says, helped nurse him back to vitality. If he ever publishes an autobiography, he thinks he should call it "The Art of Not Dying".