At first you don’t notice the family resemblance. In the elegant Halcyon Gallery in Mayfair stand two portraits that stop you in your tracks: the flag bearer and his daughter. In one, a dejected young woman huddles in a grubby Union Jack like a battle-scarred Britannia. In the second, a film star stares out from his own red, white and blue cocoon, stripped of all assets except his expression of hard-won realism. The models are Ray Winstone and his daughter Lois; the artist is Mitch Griffiths, a man who is never going to win the Turner prize.

He paints with a high-gloss realism — straight onto the canvas with oils — producing portraits suffused with light and minute detail that evoke old masters and classical frescoes thrust into an uncomfortable modernity. He gives us hoodies, self-harmers and suicide blondes, their images as sleek as an adman’s pitch. He lives in Devizes in Wiltshire, but 15th-century Florence might have suited him better. In the self-referential world of modern art, he is unfashionably figurative, a polemical portraitist who starts with an idea, finding models who can convey the thoughts he scribbles in the notebook he keeps beside his bed.

His most recent work, shown here for the first time, features the hard-man actor from Essex. Ray Winstone is stony-faced in the picture; in conversation with me he is a big old pussycat, but whenever the camera was turned on him, his expression tightened into that familiar, bankable menace. “I had to tell him to soften it,” laughs the artist. The Flag Bearer is a gem in Griffiths’ new show, The Promised Land, which opens later this month. Is it an image of right-wing bigotry, of proud patriotism, or just of an actor wearing another costume between shooting the films that have made him a better export than the Jaguar XKR parked outside his (very big) house in the country?

“To me, Ray epitomises being British,” smiles Griffiths. “He’s someone people think has achieved a lot, but anyone could talk to him. He’s one of ours going over to Hollywood. He doesn’t see himself as a celebrity.”

Griffiths’ core subject is Britishness, the pursuit of identity in our post-colonial melting pot, the tainting and trashing of the sceptred isle, its use in thrall to the fast buck of celebrity, its self-obsession as ugly as an infected tattoo.

Winstone is equally dubious about the price of easy fame. “It’s all celebs, celebs, celebs and it starts to get tedious,” the actor says when I visit him at home in Essex. “People are becoming famous for being famous. Good luck to ’em. But what happens after their 15 minutes of fame? There’s going to be a nasty accident one day.”

In 2012 Winstone will be the star of another Griffiths show, Iconostasis: Portraits of Famous British People. The title is telling: in early Christianity the iconostasis was a screen that separated the nave from the sanctuary of a church, a role Griffiths sees as now being performed by magazine covers and mobile-phone screens. “People look at these icons but are separated from them.”

When told about the project, Winstone was unsure. “It felt like I was putting myself in the frame,” he says. “To me an icon is someone like David Beckham, an ambassador for this country.” But since there is to be a charitable aspect to the show, he eventually agreed, and suggested Keira Knightley, whose portrait — fully clothed, despite excitable internet rumours — is nearly finished.

“I wanted Keira in the [Iconostasis] show,” says Griffiths admiringly, “because she’s achieved so much. In 2008 she was the second-highest-paid actress in Hollywood, and she was only 23.”

He is also painting Bob Geldof on horseback as the ancient Celtic deity Lug. Why? “My first memory of Bob was when he swore on Live Aid in front of millions. I was watching with my parents and was mortified, but my dad just turned to me and said, ‘That guy can say what he bloody well likes!’ He has such unique status in society, he’s almost a mythical figure. I might paint him decapitated and holding his head.”

Certainly Griffiths’ entrée into the world of celebrity has paid dividends; his paintings start at £40,000 and can reach £200,000 apiece. Once collectors start to chase his work, the rewards will be even greater. Right now he is working on a self-portrait called Artist Holding the Head of Brad Pitt — based on Caravaggio’s David Holding the Head of Goliath — in which he holds up a magazine with Pitt’s face on the cover. “To me, magazine covers on newsagents’ shelves are like decapitated heads. I chose Brad as he is seen as a ‘giant’, almost feared among normal men because of his looks and success.”

The Muse Is Dead, meanwhile, echoes a classical pietà: a sinuous blonde model lies naked (apart from high heels) and lifeless in the arms of a peculiar band of paramedics, her head thrown back, anaesthetised by narcissism. “She could be anyone from Britney Spears to Madonna,” says the painter. “Is she dead or just being restyled? Is the doctor a plastic surgeon or a pathologist? You can see he’s performing a breast implant on her.”

His star, however, is Winstone, who knows nothing about art, but — you guessed it — knows what he likes. “I’d love a nice Constable of the English countryside, but that’s millions and I don’t want a replica. I wouldn’t mind if someone done a fake one, though.” When he first saw Griffiths’ work, the verdict was instant: he’d never seen “anything as f***ing good as that”.

To reach his farmhouse in rural Essex, where Griffiths came to photograph rather than sketch Winstone for the portraits, you travel first to unlovely Harlow, incubator of the artist’s worst urban nightmares. In a few moments, however, you are in the Essex countryside, where well-heeled villains roost in chichi pubs and Winstone’s youngest daughter, eight-year-old Ellie-Rae, attends the local primary school. In the homely kitchen, there are fags on the table and a bottle of Jack Daniel’s on the side, the remnants of last night’s dinner party, and the talk-show host Jeremy Kyle is lecturing the lumpen on the telly. “That’s what it is these days, England,” groans Winstone, looking more Epping than LA today in tracksuit and woolly hat.

Lois, a 28-year-old singer with the hip-hop trio Crack City, lives in the converted stables, and her dad wants to build a “Georgian house” next door. On a cold early spring day he makes me a mug of brick-red tea (Earl Grey and his reputation would have been in tatters) and tells me he has never been painted before, didn’t much fancy it, but that Mitch’s talk of reclaiming the flag had got him all fired up. The two men may seem uneasy collaborators, one a soft-spoken artist from Devon who is not nearly as famous as he should be, the other the professional geezer who has travelled from a council flat to having a replica Stonehenge at the bottom of his garden and his own pigs. When Griffiths approached him about his show The Promised Land, Winstone was instantly enthusiastic. “He said, ‘Let’s make the flag something to be proud of,’” the artist recalls.

On St George’s Day the actor attends a “do” at the Dorchester hotel. “On my journey I go along the Embankment, up to Buckingham Palace, then round the corner to the Dorchester and I don’t see a single cross of St George. Epping Council once said it was causing offence to put up the flag in the village. That really pissed me off. It’s like saying, ‘Let the BNP have the Union flag!’ But no, that’s our banner, and it stands for all that is good in this country. This is our land.”

The Union Jack flutters, sags and comforts in much of Griffiths’ work, not the emblem of national pride waved by Maggie as the task force set sail, or the excitable nostalgia of the BBC Promenaders, nor even the sad symbol of no surrender you see on embattled council estates. “It’s the flag representing conflict and experience,” says Griffiths, “the state of this nation and what it’s been through, what it suffers every time someone has a snipe at it. My images are more positive than flag-waving, because the models are actually wearing it.”

Forty years ago the schoolboy Winstone twice wore the flag when he boxed for his country. Despite his patriotism, he believes the country is “not that great any more”, too beset with drugs, crime, immigration issues. His disappointment with the ruling class was confirmed on a holiday in Scotland — in Tarbert, near Loch Fyne — with an East End “barrow boy” friend and their families. Invited for drinks to the home of a future political grandee, Winstone was asked his views on social disintegration. When the actor brought up the issue of drugs, his host took umbrage and drew the party to a close. “A couple of years later, his boy was nicked for drugs. It taught me these people running our country don’t know what’s going on.”

Meanwhile, our national flag has been reduced to a liability. Last year airport police at Heathrow were banned from wearing British Legion Union Jack badges in support of the troops, although they succeeded in their appeal. This is the jumpy, fearful background against which Griffiths paints his state-of-the-nation tableaux, seeking to rescue the flag from its dubious associations and the embarrassment that even the mildest patriotism evokes in the liberal classes. “When do we really see the flag these days?” asks Griffiths. “We see it draped over the coffins of young men who have died fighting for their country.”

Winstone grew up in a council house in Plaistow, east London, where every Christmas a picture of the Queen beamed down, as the family Noël Coward would have patronised as “this happy breed” gathered to watch her speech. “Every Sunday you’d go and see your granddad and nanny in the Lansdowne working men’s club in Hackney. All your cousins and all your uncles and all your aunts would come. Everyone would wear a shirt and tie. That was your family. You’d know everyone in your street. My mum would make dinner for the old gal across the road. It was like a real community. That’s why I like living in a village now. I remember the first black man moving into our street in 1962, an old West Indian in a zoot suit, and we used to follow him down the road and touch him for luck.

“Things change. In the next box to mine at West Ham is a bunch of Muslim guys with their kids. They’re Bangladeshis and West Ham fans. So who are my mob? Anyone who comes here, wants to be British and embraces this country I’ve got no problem with. But I think you have to be able to talk about immigration. There was a Rastafarian who used to stand outside Chelsea football ground selling the British Movement [a neo-Nazi group] paper. No-one would go near him. They thought he was mad. And he said, ‘No, I want you to read it, because if you don’t read it, you have no argument.’”

He left Edmonton County School with a CSE in drama and “a kick up the arse”. “I was asked to leave the premises. I was a bit of toerag, to be honest.” He was also famously expelled from the Corona Stage Academy for attacking the principal’s car. “I done her tyres. She was horrible to me.” His teenage years were larky, edgy, smartly dressed as a skinhead in his two-tone Tonic suits and velvet-collared Crombies, but he was always a decent boy at heart.

“When I lived in Enfield, England had just got knocked out the World Cup by Germany on penalties. Me and my mate were standing outside with a can of beer and I heard a woman in a block of flats scream and a TV come hurtling through the window. She was getting a beating over a football match. A football match! And once in Plaistow, me and my mate Tony Yates were driving along and there was a young girl getting a complete beating off her boyfriend. We pulled up, jumped over the wall and told him to leave off — he was killing her. The girl took her shoe off and hit me head with a stiletto and told me to mind my own business. But you get involved. You have to.”

Winstone has had huge success bringing poignancy to even his most unpalatable characters, like the alcoholic wife-beater in Nil by Mouth. But he insists he would have been just as happy if life had dealt him the future it once seemed to offer: building trade, black cabbie, fruit-and-veg seller down the markets like his dad — whatever, as long as he had his wife, Elaine, his family, his team, his country right or wrong. Even his pre-filming diets are patriotic. The latest is a two-week Royal Marines regimen: three eggs in the morning, three eggs at lunch, three eggs for dinner and a steak every other night. “You lose two stone in two weeks. It keeps you strong. You’re in the marines, you have to be strong. After five days you start training. And then,” he laughs, “I’m going to look like an Adonis.”

Actually, he looks more Adidas than Adonis today, but whether in his trackie bottoms, or out on the town in his bespoke cashmere overcoat, or even in his tattered old Union Jack, he just looks his true self: a reformed toerag, doting dad, diehard partisan — and as English as a chicken-in-a-basket boozer. He is a fitting centrepiece for Mitch Griffiths’ show about a promised land because he truly believes that, for all its faults, we still have one to call our own.

• The Promised Land is at the Halcyon Gallery, London W1, from April 29 to June 5

The work of contemporary artist Mitch Griffiths apprehends the viewer through a dissection of twenty first century existence.

Richly  detailed, viscerally layered canvases disclose scenes which simultaneously examine notions of empire, guilt, celebrity and first world entitlement; whilst proffering to expose the essential vacuity of a society drenched in mass media and consumed by consumption itself. Griffiths employs an unflinching high realism to pick apart ideas which promise to haunt with an unnerving familiarity.