'Here's your bra, Dad'

"On a good day," says Simon Williams of his long-delayed debut as a transvestite, "I look somewhere between Esther Rantzen and Carol Channing." Which makes you wonder what he looks like on a grim day. Sooner or later there comes a point in most actors' careers when they have to stiffen the sinews, summon up the blood and start wearing women's clothes. With even Johnny Depp having a Dick Emery moment on screen recently, Simon Williams finds himself in ultra-cool company now that his time to frock up has arrived. His enduring Seventies' TV images as that glamorous Guards officer and housemaid-magnet James Bellamy in Upstairs, Downstairs and Maureen Lipman's husband in the ground-breaking satire Agony are going to take a bit of a bashing now that Williams looks more like a cross between Tootsie, Mrs Doubtfire and Charley's Aunt.

In a touring production of his own romantic comedy Nobody's Perfect, he's playing a man forced to drag up to accept a women's literary prize he won under a female pseudonym. In real life, the lanky, 6ft 4in, Harrow-educated actor still looks a bit like a Guards officer in a suit, but already he's adapting to the cross-dressing challenge with all the enthusiasm and flexibility that one might expect from some of our most distinguished Guardsmen. It helps, he says, that his 23-year-old daughter Amy, who also plays his daughter in the show, has volunteered to act as his dresser for the crucial male-into-female quick-change between scenes: "I heard her saying to a friend, 'There aren't many girls who've helped their father out of a bra.'"

For the unassuming Williams, who is married to Celia Johnson's actress daughter Lucy Fleming, the experience has been an education in the body language of gender politics: "The curious thing about all men playing women is that the first and most noticeable difference in their demeanour is that they suddenly start smiling. I did, too; so did Dustin Hoffman in Tootsie. Do women particularly like smiling?" he asks. "Or is it because subconsciously they want to please people more than men do?" Quite.

As usual in such cases, the primary source of his inspiration was maternal. "I had a picture of my late mother in my mind's eye: she was the template. And by the time I've got the lashes on and my bra and tights, I feel really quite feminine. Then I see myself in this full-length mirror next to my leading lady Stephanie Beacham, and there's this huge great prop-forward with a wig on. It's like a scene from Some Like it Hot: Stephanie is Marilyn Monroe and I'm Jack Lemmon." The title Nobody's Perfect was borrowed from Joe E Brown's pay-off line at the end of Billy Wilder's masterpiece. "Kiss My Aunt was the play's original title, but it proved to be a nightmare with the box office staff because everyone kept mishearing it."

The son of actors-turned-playwrights Hugh and Margaret Williams and the younger brother of poet and sometime theatre critic Hugo Williams, Simon followed the late-flowering family tradition of becoming a writer himself in his late 30s. Now, at 55, he has two bestselling novels and three plays - one thriller, two comedies - under his belt, relishing the chance to combine "the solitude and power" of writing with the camaraderie of acting. "But I'm better at taking criticism as a writer," he admits. "With an actor, what's being criticised is so much a part of him that he can't extricate it, really."

It also makes sense to generate work by creating roles for himself now that posh-sounding actors can get stranded on Planet Toff these days, surrounded by Guy Ritchie types who learn their Mockney accents at Rada. Although his wife picked up a large inheritance from the sale of her great-grandfather's merchant bank to Chase Manhattan last year, Williams continues to work as a jobbing actor.

"Jeremy Bloody Irons and Nigel Havers," he says, have cornered much of his market, although Victoria Wood cast him as a bacon-butty-fancying royal visitor in her BBC1 sitcom Dinnerladies. "I wish I sounded a bit less distinctively toff," he admits. "It puts you into a pigeonhole. There was a time when public-schoolboy actors were all betraying their origins and adjusting their voices. I thought, 'I'm not going to do that' but now, looking back, I regret it.

"I've been shackled to James Bellamy for 30 years, and promoting Upstairs, Downstairs in America always felt a bit of a betrayal: we weren't allowed to say that England isn't like that any more, that we're not all class-ridden and tight-arsed." Yet there's nothing like foreign productions of a play about English tranvestism to reveal how the world really views us. In the current German and Italian runs of Nobody's Perfect, they have refused to change the English setting. That's because, explains Williams with a grin, "they think transvestism is an English disease."

Nobody's Perfect