It is six ’clock on a weekday morning, and I am sitting on Rupert Everett’s elegant white sofa in his equally elegant wood-panelled drawing room in Bloomsbury while he prepares himself for a day of filming his latest role, as Miss Fritton, the headmistress of St Trinian’s.

Rupert is reading a book by the Indian philosopher J. Krishnamurti and quotes me selected extracts. “What is life?” he says. I look blank, feeling somewhat unprepared to discuss spiritual matters this early in the day. “Not all the things that we go through,” he continues, “power, position, prestige, fame, or no fame… that’s not life; that’s part of our mishandling of life.”

I am distracted by the green plastic cart of Shrek toys on the wooden parquet floor, a by-product, presumably, of his recent reprisal of the role of Prince Charming in Shrek 3. Possibly infuriated by my inattention, Rupert snaps the book shut, and pulls another one down from the shelf, containing the original St Trinian’s cartoons by Ronald Searle, showing a variety of gin-swigging, cigar-smoking schoolgirls, apparently hell-bent on wreaking havoc with their hockey sticks. “St Trinian’s — defender of anarchy,” he says, “like me…. Just remember, one man’s terrorist is another woman’s freedom fighter.”

And with these somewhat conflicting thoughts for the day, we depart by car for the film set, a dilapidated mansion in Buckinghamshire. On the way to the set, Rupert eats three Cadbury’s Creme Eggs in between puffing a small roll-up. Then he flicks through the pages of Hello!, giving an acerbic commentary on the celebrities featured within. “Forget St Trinian’s, I should really be the headmistress of a star academy. All these so-called style divas have such terrible dress sense.’

His voice becomes increasingly disapproving, his dark eyebrows raised ever higher, as he regards an assembly of female stars at a New York ball. “I could give them a proper going over, and then put them back on the road. Ooh, look, Kate Moss’s hands have become almost as grabby as Madonna’s. Actually, they’re all at it, clutching their handbags with knobbly claws, like it’s stuffed full of cash. That will have to be one of the first week’s lessons at school. How to hold your handbag without looking grasping.’

IN FINE FETTLE AT 48

By the time we reach the location — a Home Counties gothic monstrosity, surrounded by fields awash with mud, through which crocodiles of little girls pick their way, dressed in St Trinian’s uniforms — his demeanour is increasingly headmistressy; polite, yet with the potential to catch one out. He sweeps into his trailer, strips off his black tracksuit, revealing all six foot four of himself in naked glory, complete with rippling six-pack stomach, bulging pectorals and remarkably muscular torso.

At 48, he is still handsome, but he nevertheless regards himself with more than a little discontent, and remarks, “I’m thinking of having a pubic lift, and maybe a face lift, too, with some rather visible, neatly tailored scars, like the seams on a suit. Oscar Wilde said the tragedy of all women is that they turn into their mothers, and the tragedy of men is that they don’t. Update: the tragedy is that everything droops.”

Then he wriggles into his Miss Fritton costume: a large quantity of pale pink undergarments, two enormous plastic breasts, and a floral and tweed outfit of the kind worn by royal ladies of a certain age. Once his make-up has been applied and his wig fitted, he looks uncannily like Camilla Parker Bowles, and reveals a similarly shapely pair of legs.

Sadly, Rupert’s co-star, Colin Firth, who plays Geoffrey Thwaites, the Minister for Education, is not on set today, so I cannot quiz him on the progress of their on-screen affair, though I do sneak a look at the photographs that show the pair in bed together, engaged in a passionate kiss. Rupert declares that he and Firth — whom he has christened ‘Frothy’ — are getting on terribly well, “especially now that we have finally been united as lovers. Although I think Colin took it a little bit too seriously — he wanted to do take after take of the snog scene. I suppose he’s always been rather in love with me.”

He pauses, and gazes at his female reflection in the dressing-room mirror. He looks morose, just for a few seconds, and murmurs to himself — or rather, to Miss Fritton — “the game is up”. Then he glances at the photographs pinned around the mirror of the various supermodels, Hollywood starlets and pop singers appearing as St Trinian’s alumni (Lily Cole, Mischa Barton and Girls Aloud, for starters).

“It’s just as well I’m gay,” he says. “If I was straight, I’d be a hopeless mad movie star who f****s everything that moves. That’s what I’d be like — married to every single girl that I’d worked with, on wife number 10 by now, always being sued for divorce because I’d been caught with two chicks somewhere… Or I’d be like a rapper — three girls at the same time, coke, orgies, yachts. I would be a monster, actually. I’d have to be competitive on a lad level with all those other male movie stars. I’d probably be an alcoholic, too. Mind you, I’d have made a lot more money — 20 times more money, probably.”

He sighs, adjusts his bosoms, pats his blonde wig, and heads out of the trailer to film his next scene. “After this, I’m disappearing,” he says, over his shoulder to me.

“Back to London?” I say.

“No,” he snaps. “The Gaza Strip.”

BORN TEASE, NATURAL ACTOR

Some weeks pass before we meet each other again. At one point, he calls me from Moscow, where he is on a UN charitable mission (“Do stop probing,”); a little afterwards, from the Swiss Alps (“I’m in need of a dose of fresh air”); and then from Berlin (“Don’t ask”).

Meanwhile, I am beginning to despair about writing this article, and I ring Colin Firth, who clarifies a number of points. “The St Trinian’s bed scene rather surprised me,” he says, in tones of mock-seriousness. “Rupert turned into a giggling schoolboy. He was adamant that we shouldn’t kiss; I was adamant that we should. But the chemistry was definitely there in the end.”

As for his youthful self in Another Country, he says, “... One was very easily seduced by Rupert. And he was much more worldly than me — I thought I was sophisticated, until I met him. But I think we’ve grown towards each other now — I’m less earnest, he’s more radical. And we do work well together. Or maybe we’re stuck in some diabolical vortex, Rupert and I…” He laughs, and so do I, though I am beginning to wonder whether Rupert has in fact disappeared into a diabolical vortex of his own making, leaving the rest of us behind.

Eventually, he surfaces again, as always, and we meet for a drink in Claridge’s. He has shaved most of his hair off, revealing some terrifying-looking scars on the back of his head; when I ask him what happened, he says, enigmatically, “Scars from life’s gay battlefield, darling.”

Still, he is slightly more forthcoming on the subject of his latest projects — he has written a film script with a friend about the last days of Oscar Wilde (a script which is, according to Firth, “the best thing I’ve read in years — Wilde has been so neutered by china teacups and repertory companies, and Rupert has put the balls back into him”); and is now contemplating having a Romanov eagle tattooed across his head. “Then I’m disappearing again,” he says. “For a year, possibly.... I’m not planning on murdering anyone. Well, only my career…”

This is a rather astute piece of self-analysis, if partly tongue-in-cheek; for while he has proved adept at sustaining his career, despite coming out as gay in a profession that might have preferred to keep him as a heterosexual heart-throb, he is also more capable of subversion than any other famous actor I can think of, a talent that extends to subverting himself. It’s what prevents him from taking himself too seriously — his likeable self-deprecation makes him the opposite of the stereotypical egocentric movie star — but his anarchic streak runs deeper than any St Trinian’s schoolgirl.

Now, as St Trinian’s is about to open, he seems restored to his usual cheerfulness. “Darling,” he says, sympathetically, when we meet for another drink, “it must be ghastly being a woman. I had no idea of the nightmare of wearing heels. They’re so bad for the back. I’m definitely not wearing them for my next role.”

When I remind him that it wasn’t so long ago that he said he didn’t want another film part, he looks at me with genuine surprise. “Don’t be so ridiculous,” he says. “I love acting. I came out of the womb looking for an agent.”

He’s right, of course; for Rupert Everett is a natural actor, and a born tease, as well.