Natasha Thoday has a remarkable CV. In her 35 years she has been a teacher, a cabinet-maker, an industrial designer and an inventor of groundbreaking audio speakers and amplifiers. She has gutted her five-storey terraced home and rebuilt it herself from scratch. She has competed in triathlons, undertaken 350 scuba dives and travelled to almost 30 countries. She has written learned articles for technical magazines and designed a range of spiral staircases. And in her spare time she plays the flute.

It reads like the CV of an entire staffroom. It makes you wonder how she has found time to be a teacher. And, more than that, how she found the time to transform herself from a male teacher to a female teacher.

Transformed she certainly is. The imposing six-foot figure I meet in Brighton, her home town, is most definitely a Miss. The voice is fairly deep and the shoulders wide, but this is no drag queen. Jewellery is modest and make-up barely there; she has sensible mules on her feet and tumbling raven curls frame her face.

She wears a tight beige skirt and a clinging top that reveals modest cleavage. A modern working woman.

Natasha Thoday found fame last week - not to mention pound;3,700 in compensation - when she won an out-of-court settlement against Telscombe Cliffs primary school in East Sussex, which terminated her employment as a supply teacher at the school after just one day. She drives to our appointment in her Mercedes, bought with the settlement money.

She was not at school last week; she was at the Labour Party conference with a group of other transsexuals, lobbying MPs to grant them full legal and civil recognition. Among many other issues, transsexuals in the United Kingdom are denied the right to change the gender shown on their birth certificate.

So what does Natasha’s birth certificate say? Nicholas? Nigel? Noel?

“I’m not telling you,” she says politely. “It’s not relevant. I’m not that person any more.”

It’s the only question she refuses to answer. For the rest, Natasha will tell you every last detail, so determined is she to fight the cause, and use her own life as ammunition. That’s why we are on Brighton seafront, talking about a six-year-old boy who gradually realised he should have been a she. “I knew there was something wrong, but for a long time I didn’t realise what it was. I was a solitary child; I didn’t like team sports.”

What the little boy did like was dressing as a woman. “It wasn’t until I hit puberty that I realised it was ‘wrong’. I felt so guilty, and for years I struggled to hide it.”

That long struggle may be the reason why Natasha’s CV is so impressive. “People in my position tend to overcompensate by hurling themselves into other areas of life. They become mountaineers or polar explorers in a vain attempt to prop up this identity that doesn’t fit.” If Natasha could say she was a scuba diver or an engineer or a triathlete she wouldn’t have to face the more troubling question of whether she was a man or a woman.

The possibility of a sex change first entered her mind soon after she moved to Brighton 15 years ago. “I saw an article in the Sunday papers about a transsexual. My jaw hit the floor. I thought, ‘Jesus, I’m one of these’. I freaked out, but I kept the article. I hid it, and took it out periodically to re-read it. But I was in deep denial, and I opened every single door - just look at my CV - to fight the reality of what I was.”

The struggle went on through Natasha’s PGCE at Brighton Polytechnic in 1986 and her subsequent early career as a teacher. “My life was crashing. I spent the 10 years before transition like a glider running out of air, slowly spiralling down into deep depression. I didn’t know what to do.”

The long, dark period of depression, the years of secrecy and shame, ended three years ago. “I had started reading stuff on the internet. Secretly, of course. I’d copy stuff on to disks, then hide them. I hid them so well I still can’t find some of them. The secrecy is horrible. That’s why, today, I would never tell a lie like that about myself.

“I began to realise I wasn’t alone. All the advice I read was to go out and meet other people like myself, so that’s what I did. I decided to see my GP, and I went armed with all this information. I told him: ‘This is what it’s all about. I’d like a referral to Charing Cross gender identity clinic - and I’d like it now please.’ ” Within a few months, Mr Thoday was on hormone treatment and on the way to becoming Ms Thoday. It was a revelation. She jabs a painted fingernail at her chest and says: “All my life I’ve imagined I had a kind of valve right here, pumping out a constant flow of fear and anxiety into my body. Within hours of my starting the hormones, that tap was turned off and the anxiety disappeared. It was an indescribable relief.”

Late last year Natasha went to her bank, took a pound;6,000 mortgage extension on the house she had renovated, and flew to Bangkok for some renovations on herself - the “snip” as she jokingly calls it, followed by reconstructive surgery to form a vagina. “What goes on between the ears is more important than what goes on between the legs, but that was the icing on the cake,” she says.

During her hormone treatment Natasha was spending more and more of her time “en femme”, as she puts it, when at home, but carrying on as Mr Thoday in public - and Sir at school. “I’d get up in the morning and put all this male stuff on, go to school, then come home and get rid of it all.”

Her first public outing as Natasha was on a trip with transsexual friends to Amsterdam. That day she decided to become Natasha full-time.

After recovering from the operation she wanted to teach again - but not at the schools that had known her as a man. She signed up with a supply agency, Teaching Personnel, based in Hertfordshire, and worked in several Sussex schools early this year without incident. “The agency would tell schools: ‘Natasha is a very good teacher, she has an excellent reputation - and, just to let you know, she’s a transsexual woman.’ Leaving the legal issues aside, the school would then decide if it wanted to book me. There were just a few refusals at the beginning.”

In March, Natasha arrived for her first day of a three-week booking at Telscombe Cliffs. One boy taunted her by calling her “Sir” and a girl was heard to ask whether Miss was like Hayley, the transsexual in Coronation Street. But Natasha was used to this, and felt the day went well. She was particularly pleased to get a round of spontaneous applause after reading a dramatic passage to her class. That evening at home her agency called to tell her the school didn’t want her back.

She was determined not to let matters rest. She took action under the Sex Discrimination Act and won the out-of-court settlement. The school’s head, Andrew Kearsey, won’t comment on the case but a spokesman for East Sussex county council says the school accepts there was a breach of the law. The council will be sending a circular to all schools in the county reminding them of their obligations under equal opportunities legislation.

Natasha is thrilled at the result - and the publicity - and has no qualms about returning to school when her agency next offers her a placement. “Yes, it’s a battle every time I go into a new school, but someone’s got to fight that battle.”

How does she answer those who say the classroom is no place for a transsexual? “Look, it’s not contagious. You can’t catch transsexualism. The official figure is one in 10,000 people. You don’t learn to be a transsexual any more than you learn to be a black man.

“Children are honest, and they don’t like to be lied to. It’s important not to feed them my ideas and language about an issue like this, but if they ask questions I will try to answer them honestly at their level.”

What about colleagues? Natasha says many don’t realise she is transsexual. “It hasn’t been an issue. Adults are less forgiving but also less intuitive and perceptive than children, so I find I can go anywhere in public and, as far as I know, people take me for a woman. It’s the same in the staffroom.

Parents? “I’ve heard from deputy heads that parents have occasionally phoned up to complain, but in every case the school has supported me. If parents are concerned, I am prepared to lean over backwards to speak to them and give them all the information they want.”

Teachers also have personal lives. I ask Natasha if she has a boyfriend. “I think men are frightened of me. I have high standards too. I don’t want just anybody. I’m prepared to wait. I’m very busy, and I’m happy for the first time in my life.”