Mike Leigh is in a cheerfully bullish mood when I meet him at the Soho Hotel. ‘Have you read today’s Guardian?’ Dammit — I should have seen that coming. ‘A guy in G2 would like to sue me for defamation of Ruskin!’ He seems almost pleased. His characterisation of the great critic as silly and effete in his new film, Mr Turner, does seem a little ungenerous. Ruskin did more for Turner than anyone. ‘That’s true,’ says Leigh. ‘Working with the brilliant young actor Joshua McGuire, I started to think how Ruskin was incredibly spoiled and cosseted by his parents… He was a prig!’ He emphasises the ‘g’ in ‘prig’ for the avoidance of doubt. ‘Turner undoubtedly had reservations about him and took the rise out of him. But the idea that the characterisation is a gratuitous pratfall is nonsense, really. There are guys like that.’ He looks at me askance. ‘You probably know them.’

At 71, Leigh is arguably our greatest living filmmaker, with his own subtle idiom and cross-genre work from the comedy of Abigail’s Party (filmed 1977) to the heartbreak of Secrets & Lies (1996) to the comic opera of Topsy-Turvy (1999). It’s not entirely crass to call Mike Leigh the British Woody Allen (or Woody Allen the American Mike Leigh) for their shared belief in improvisation, the comedy and sadness in their films and their having won every type of golden statuette going. But in their late style they diverge. While Allen is becoming dangerously trite, Leigh has moved into a rich new key with Mr Turner, a biopic of the painter that offers a cinematic box of delights while retaining Leigh’s trademark realism.

And yet, making Mr Turner without his long-term producer Simon Channing Williams, who died in 2009, he was unable to raise the funds to shoot two key scenes: the burning of the Houses of Parliament, which Turner witnessed and painted, and Turner in Venice. ‘I regret the loss of Venice more. It was a tragedy. It no longer is a tragedy because we’ve made the film we’ve made. There was a crunch moment in our office when we realised we would not get more than £8.3 million.’ (A budget that would have to be multiplied 13 times to reach the cost of one Harry Potter film.) ‘It came down to: are you prepared to make the film and not go to Venice?’ He shrugs.

‘It’s an occupational hazard. Sure, it would be nice to get more dosh, but it’s the price you pay. Here’s the thing — backers insist on a name, and that means an American name. There are plenty of sources I could go to, and they’d say: get Johnny Depp to play Turner and we’ll give you as much as you want. Well, no disrespect to Johnny Depp, but I don’t do that.’ Timothy Spall, Leigh’s long-term collaborator, was always going to play Turner; he had already been taking painting lessons for two years.

‘There is world cinema, which is what we all do from here to Japan, and then there is Hollywood. It’s a different planet, and it’s got nothing to do with the rest of us.’ Why is Hollywood’s influence so disproportionate? ‘From the first world war onwards, they spotted it [cinema’s potential] and bought distribution and exhibition and owned screens. They got fed up with the weather in New York and all went off to this sunny place and this thing grew, a whole city which is only about film, so it makes films about itself. It’s got nothing to do with what we do, which is to make films about life, about the world!’‘I’m committed to independent, indigenous film. I’ve made 19 full-length films and no one has interfered with a frame, never ever. Because the minute there’s a threat that anyone wants to put their fingerprints on it, I walk away. I don’t complain. I really don’t.’ He folds his hands across his paunch with true satisfaction. I volunteer that Hollywood would not tolerate the film’s suggestions and loose ends. He goes further.

Love, death and Mithraic pronouncements (‘The Sun is God!’ gasps Turner, before expiring) are all in Mr Turner, along with some suitably epiphanic skies. ‘Obviously, if you make a film about Turner, you become more and more acutely sensitive to the whole issue of light,’ he says, gesturing to the October shadows. It is the first full-length film that Leigh has shot digitally, and he and his long-term collaborator, cinematographer Dick Pope (who won the Vulcan Award for Technical Artist for Mr Turner at Cannes this year), used CGI to add painterly effects of light. ‘The film is full of them,’ says Leigh, but the only totally ‘concocted’ vision is the retired warship, The Fighting Temeraire. He and his crew still got up at 4 a.m. to capture the dawn, he hastens to add.

As a former defender of celluloid, Leigh feels the need to eat a certain amount of hat. ‘To my embarrassment, I remember being at a little industry screening in LA, which was packed, where I talked passionately about film, and how editing on film has the right rhythm. And everybody cheered! It’s all rubbish. Rubbish. Editing digitally is great. The technology has been updated with great sensitivity to the needs of filmmakers. Look, laboratories are closing down; everything’s heading in that direction.’

At this point I make the mistake of calling Mr Turner ‘more cinematic’ than his previous films. ‘I reject the idea that anything can be more or less cinematic. Cinematic is cinematic. A close-up of a person in a small room can be cinematic. You can’t see for example my film Meantime as being less cinematic than Mr Turner because it’s about grotty flats and dole queues…’ I sense I have riled him by implying a conservative hierarchy of art, with royal academicians at the top. Of course, I reply, the imagery in Meantime (1984) is cinematic — its plastic bags circling in the wind and so forth, and the eerie self-propelling pram. Leigh’s sunshine returns. ‘There was a guy pulling a long piece of catgut to make that pram move.’ Mollified, he adds: ‘I concede you may be right. What we’ve done very deliberately is embrace Turner’s paintings and allow them into our bloodstream.’

Love comes to Turner when, late in life, he meets a Margate landlady called Mrs Booth. He goes on to create the work of his extraordinary late flowering. The role of Mrs Booth is played to perfection by Marion Bailey, Mike Leigh’s partner. Does love help Leigh to achieve new work? ‘You’re very cheeky, I must say,’ he grins. I’ll take that as a yes.