Friendly and magnanimous man who comes but once a year over snowy towns and Christmas trees, dipping into his sack of gifts. Dignified and deep-voiced postman cum chimney sweep who works during the season of goodwill and commercialism. Ebullient and jolly gentleman with rosy cheeks. Or sceptical, curmudgeonly and grumpy schizophrenic who is part cultural attache and part million-dollar mogul.

Enter, on an environmentally friendly sleigh, Father Christmas. ‘I’m also known as Santa Claus,’ he says, smacking his reindeer on the bottom and turning off some particularly nasty electronic Noel bells. ‘I don’t care what you call me. And I’d rather have a Saab.’

We’re sitting in Riva, one of London’s most fashionable Italian restaurants, in which Santa’s hero Grey Gowrie dines – Santa’s choice of eaterie. He points out that the food is excellent and that he used to be called Father Frost in what was the Soviet Union. ‘For political reasons.’ He picks a particularly beautiful snowflake earring out of his sack, ‘From Manguette, London’s best costume jewellery shop,’ he says, curiously indulging in some product placement.

He’s wearing a Father Christmas robe – a horrid synthetic white and red coat of the type favoured by cheap impostors in the Harrods grotto, and a wide black belt and coal-coloured boots.

It’s fake fur around his hat. ‘That’s not because I’m ecologically minded but because I spend most of the bloody year sorting out presents. This is all I could get my hands on,’ he says, shooting me a look through a gritty, baleful eye and taking a bite of grilled radicchio with extra virgin olive oil on it. ‘Makes a change from frigging cheap mince pies and cooking sherry,’ he says.

He carries a piece of plastic holly and is covered with snow from a spray can. What does his look say about him? ‘That I have to live my life as if I were on camera the whole time. Worse than that, as if I were on Wogan 24 hours a day.’

He looks crossly at the couple sharing some beetroot gnocchi at the next table. The man who has been accused of being a figment of the imagination, a creation, or nothing more than a story for children, spits as he speaks and says that you don’t get beetroot gnocchi in the North Pole.

It has been said that his garb reflects fetishistic obsessions. ‘Oh, yeah,’ he says, looking visibly discomfited and letting out some unpleasant gas. ‘I suppose you’re going to ask me next whether I Saw Mommy Kissing Santa Claus was based on fact.’ He laughs, a bronchial laugh, and his beer belly heaves. So how does he see himself sexually? ‘I think the fact that I romp through the bedrooms of Britain and come down chimneys proves, irrevocably, that I am a sex symbol.’

He is a hard person to read, and it is difficult to tell whether he is being sardonic. ‘I regard the Press as the greatest menace in my life. They are always trying to prove I don’t exist. Now I suppose you’ll be doing a Santa in Sex Romp type headline. Ho ho ho,’ says the man whose department store imposters spend their time luring tots into grottos and getting children to pose in their laps.

Father Christmas has a flowing white beard, white moustache and massive white locks. ‘What do I think of myself physically? I think I’d look at home sleeping in a shop doorway along the Strand.’

He says he feels rather embittered that he’s unable to change his image. ‘I have to look like this.’ He says he’s restricted in his looks, imprisoned by people’s expectations of him. ‘In much the same way as there’d be outrage if the Queen turned up to a party wearing a bondage outfit.’ He has a hangover, but takes a generous slug of his Barolo wine. ‘D’yer know’ – he flicks some dandruff off his shoulder, pretending it’s snow spray – ‘I once got lockjaw from keeping a fixed grin?’ That was in the days before he went to Santas Anonymous, a self-help group for Father Christmases. His polenta with fegato in sage and a side portion of porcini arrive.

Father Christmas surprises. He doesn’t look, smell, or even eat the way one might expect. Underneath the slightly aggressive bravado, one senses a cautious man. Perhaps a lonely one too. But the thing that most strikes one is his incredible age – he is 142 years old. One suspects he would like to be retired. (He once said in his Day in the Life profile in The Sunday Times that he found his life ‘cold, disagreeable and lonely’.) In addition, he also shows an unexpected and scholarly interest in Nordic literature and 16th century Russian icons.

‘I give more free handouts than the DHSS, ho ho ho, and I run my worldwide operation on my own. So I guess I’m pretty entrepreneurial,’ he says. ‘I’ve faced an awful lot of vicissitudes, but I do have a will and zest for life.

‘You know, it’s a filthy job. People think I’m patriarchal and heterosexist – and I’m not. I’m quite wise, but I’d like that to be off the record,’ he says, starting to help himself to my duck.

‘Obviously everyone knows I have a history of alcohol abuse in my family. I mean you don’t get a red nose and a gut like mine by looking at Perrier,’ says the man who is clearly drunk in every picture ever seen of him. ‘I guess that’s why I often snore on the job.’

‘What else? Isn’t that enough . . . I’m interested in child psychology. I guess I’m a bit like God,’ he says, modestly. ‘I mean, children think I’m wise, and bearded, and come out of the sky. Personally I think I knock spots off God. And I’m the most successful promotion story since Jesus Christ.’ What of his childhood? Was it a happy one? ‘Well,’ he says, clearing his throat, ‘my ancestor was St Nicholas (Bishop of Myra in the Province of Lycia) who lived in the middle of the fourth century.’ Santa arches his back and looks proud. ‘There were once more than 400 churches dedicated to him in England. He was the most popular saint the Christian world has ever known.’ It seems Santa doesn’t want to talk about his parents, if he ever had any. So in a rare fit of yultide charity, I let the subject drop. Is he kind? Santa looks out of the window. ‘Oh, look, there’s a Saab.’ Or grumpy? He raises his eyebrows. ‘Do you know, I’m part of the dependency culture. And I have a fantastic ability to help people overspend.’ Yes, yes, but is he grumpy? Oh dear, Santa’s drunk.

How does he feel about his impersonators? ‘What!’ he booms. ‘Those people walking the floor of department stores, hardly being paid. Impostors!’ he says, taking a swig of his cappuccino and getting the froth caught in his beard. ‘I bet they can’t claim the nationalities of various different countries.’ He smiles. ‘They’re not committed European federalists.’