I usually wear flat shoes and casual clothes, but for this interview with Eddie Izzard I turned up in high heels, looking distinctly 'feminine' in a long narrow skirt, silk shirt, jewellery, the lot. I had heard that Izzard, who is openly transvestite, often wears high heels, mini-skirts, make-up and nail varnish - and I don't care to be upstaged by a man. Imagine my surprise when he opened the door of his flat wearing a crumpled (man's) white shirt, (man's) jeans and flat (men's) shoes, with no sign of the famous transvestism apart from a full set of long but unvarnished fingernails. Serves me right.

He is shortish, with untidily dyed blonde hair and a rumpled face that looks as if he had had a string of late nights. He likes wearing clothes that cross sexual boundaries, though he won't call them 'women's clothes' because if they belong to him and he wears them they're his clothes, and he's a man. He enjoys the way they look and feel, but he also enjoys confounding people's preconceptions. He certainly confounded mine.

I have never interviewed a stand- up comic before. I had expected him to be fast-talking, extrovert, weaving through a stream of polished anecdotes. I was worried in case I didn't find him funny. He didn't even try to be. Instead he was serious, thoughtful, modest.

The small flat in which he lives alone was cluttered, its bathroom festooned with (male) shirts - or at any rate, shirts with buttons on the right - and underwear drying on rails above the bath. No make- up to be seen. While he made Nescafe I checked out the living room. It was filled with books, chiefly biographies of actors and politicians; Shakespeare, Shaw and other classics; also videos, mainly of other comics but also classic films; and CDs.

A black ghetto-blaster was playing loudly. The CD lying on the floor beside it was called Modern Life is Rubbish. He clicked it off before settling down on the opposite sofa.

As though he had read my mind, he says: 'I'm not attached to possessions. I've lived in this rented, one-bedroom flat for two years now, and I'm really not bothered about the house thing. It's only when I go to other people's places that I feel it might be nice to have a more, mmm, restful home environment. My mind is in these things,' he says, with a wave at the shelves of books and videos.

Izzard's career takes a great leap into the unknown this week. He is cast opposite Lindsay Duncan in David Mamet's new play The Cryptogram, about a child buffeted by the grown-up relationships around him, which starts previewing today. The play is practically a two- hander, so Izzard is on stage most of the time. His character, Del, is a man in his thirties. ('He happens to be gay, but not very.') For someone who has spent the last eight years making a name for himself as a highly original funny man and has achieved cult status as a stand-up comic - without recourse to television exposure - a straight acting role may be a risk.

Not so, he says. That was always the plan, and it explains why he has stayed away from television up till now: so that people didn't automatically start to laugh when they saw his face. The part cropped up rather suddenly, that's all, though in a most flattering way.

Earlier this year, he and the actor Alan Rickman met at a benefit at the Palladium. Izzard told Rickman how much he admired his work, and Rickman reciprocated. Shortly afterwards, Rickman turned down the part of Del but suggested to the producer that he approach Izzard.

'I got the call on Friday, did a read-through the script on Saturday and on Tuesday evening I was offered the part. For three days everything spun round.' What he finds so flattering is that Rickman should have recommended him for the part. It is, he says, the praise of his peers that matters to him most of all. He can take or leave the money and could even do without the applause; but the respect of his peers is crucial.

'At school I was quite sure I was a talentless bastard, but at 15 I got my first part in a school play and learnt the art of upstaging. Puberty and acne came along and I thought, I can't play the lead in plays, but I can do it in comedy. That was a way of hiding for me.'

His childhood was not entirely happy. He was born in Yemen in 1962. His father was working there as an accountant with BP at the time; his mother was a nurse at the refinery. She died of cancer when he was six.

'A lot of people say: that's it - that's the basis of your transvestite thing. But I had definitely been wanting to wear dresses since I was four, two years before she died. She was a very loving mother. I was a pushy kid, but if I cried in the middle of the night she never once said, 'This is ridiculous.' She would always get up and bring me a glass of lemonade. There was a big affection drop-off when she died.'

Eddie's parents had decided before her death that their sons would be best at boarding school, so he was packed off to Wales at the age of six. 'It was like being hit over the head with a sledgehammer. Occasionally I still collapse in floods of tears at the thought of it.' He sits very still, his voice drops. 'There was about five years of crying before I learnt that crying was the weak link in the totally unemotional public school system that churns out people who are numb and never really live their lives. I feel pleased that I escaped from that mind-boggling system.'

He went on to read maths and financial accounting at Sheffield University, but he left after a year.

'For five years I made my living as a street performer. Actually, I didn't make my living to begin with. It took me a year to get up and running.

'I lost all my confidence, but I kept going because there was nothing else I could do, or wanted to do.

'After doing a lot of street work I gradually realised that I could build up and use the audience's energy in a most amazing way. You manipulate their expectations. I used to do it with a penguin.'

A what? 'A penguin; actually a penguin tea-cosy. I would put it down on the ground, very, very gently and carefully, and stare at it with tremendous concentration. An audience would gather and they'd stare at it, too. I always wanted to see if I could walk away, melt into the crowd and disappear, leaving them all still staring at the penguin. Anyway, that's how you manipulate their expectations. It's a matter of concentration.'

Eddie Izzard 'came out' as a transvestite when he was 23, although he didn't begin to wear frocks and skirts and blood-red nails on stage until a couple of years ago.

'I had my mid-life crisis in my twenties. You can hide from the rest of the world or you can say, this is me, and if you have a problem with it, that's your problem.'

It seems to him unfair that women can wear whatever they like, even the most masculine, three-piece suit look, but men do not have the same freedom.

'TV (he means, as always, transvestism) just hasn't linked into society. TV people are still in a Fifties ghetto. Most TVs are repressed, and this is what women don't like about them - that when they do break out they have this teenage girl syndrome, all dressed up and way over the top.

'Even though I'm TV I happen to fancy women. I'd be quite happy to be gay, it might even make more sense, but I'm not. As to having children - yeah, I'd like children. I'd be the ultimate one- parent family.'

It isn't likely to happen just yet. He has what he describes as a 'loose' relationship with someone that has been going on for quite some time now (he protects her identity very carefully), but marriage per se doesn't interest him, except as an excuse for a good party.

Whatever he may say, Eddie Izzard would have made a good accountant. He's a great planner. His career was planned in minute detail, with very little left to chance.

True, the part of Del in the Mamet play could be called a stroke of luck, but he had already planned to move into straight roles about now.

'You need to have a strategy, otherwise the river hurls you into a series of rapids. Now I've got the bit between my teeth, and I just want to do all these things, make things, create things. I really love making things.

'I want what I do to earn money so I can make more things. I always felt I had a facility for making money, but instead of doing it the easy way - by being an accountant or financial consultant - I thought, let's do it the hard way with the creative thing.

'I was going to build up gradually from the shallow end, but along came this Mamet play and that's the deep end, off the top board.'

'The Cryptogram', starring Eddie Izzard and Lindsay Duncan, is previewing at the Ambassadors Theatre, London WC2, and opens on 29 June.

(Photograph omitted)