Big may be beautiful but small can be sexy - actress Lisa Hammond is living proof. Lisa is four feet one inch tall, and playing romantic lead Nicky in BBC2 film drama Every Time You Look At Me is her biggest break so far.

But with Mat Fraser, Britain's best-known Thalidomider, co-starring as lover Chris, viewers will be seeing a bit of TV history in the making. There has simply never been a mainstream TV fiction which has cast disabled actors in both romantic leads before.

"Mat and me had that conversation about being two disabled people getting it on in lead roles... It's unheard of - but we had to put that out of our minds and just live in the moment rather than worry about it, because that just makes you really nervous," says Lisa.

Not that it's easy to imagine her being nervous. Lisa, who spent four years as Denny Roberts in Grange Hill in the early 90s, is as feisty off-screen as she is on it, and the lip stud and tongue stud sported by Nicky are Lisa's own.

The film also features ex-EastEnders and Clocking Off star Lindsey Coulson as Nicky's mum, but it was written specially for Lisa and Mat after Lisa led a ten-minute short for BBC2 called North Face, also by Lizzie Mickery.

North Face was a brilliant little drama in which lanky Ralf Little was locked out of his flat, and the only person who could help was the diminutive young neighbour whom he once snogged and then ignored. The film was rich in what the professionals call UST - Unresolved Sexual Tension. "Ralf's character was dating another girl but it turned out we had kissed at a club, and by the end of the ten minutes we were into that 'Shall we have sex or not?' territory."

So how come she keeps getting these provocative roles? "Yeah, well, I'm probably typecast," laughs Lisa, 25. "I do get quite a lot of them, but Nicky's quite different to me as well. She's a bit more nave and her family life is very different. My mum isn't overprotective like hers - she always reckons I'm more streetwise than my sister, who is two years older and able-bodied."

Mat Fraser, most recently seen presenting C4 documentary Happy Birthday Thalidomide, appeared in another short drama in the same film season, so Lizzie Mickery had the idea of bringing the two together and writing a script drawing on their own experiences. Nicky is a hairdresser and Chris is an ambitious teacher who, apart from being 16 years older, has short arms, flipper-like hands and no thumbs. The couple cause consternation when they so much as go into a pub together. Lisa, who has been a friend of Mat's for years, knows how that feels:

"It's sort of OK in society when you're the one and you're almost treated like a mascot in certain situations, but as soon as you double up or go out with more than one disabled person, people think it's a Sunshine trip. They can't handle it, and you get aggression or pity or laughter or rudeness."

The real Lisa is not as combative as her fictional counterpart but she still finds the behaviour of strangers challenging at times. On the day I interviewed her, she had already had a bizarre encounter with a woman in a fashion store:

"She came rushing up to me and went 'Hello'. I said hello back but I didn't know her. Then she went 'I've got something for you'. And she reached into her bag and got out what looked like a perfume bottle. She said 'This is Lourdes water.'"

The stranger dabbed her finger with water, marked Lisa's arm with the sign of the cross and started muttering Hail Marys. "Then she put it on my face in a cross!" says Lisa, her voice rising with affronted incredulity. "I thought 'What on earth is this? You're harmlessly shopping in Top Shop and this happens!'

"But so many random things happen to you. Being disabled is a bit like being famous, only more negative. You can't be anonymous; you get followed around the supermarket and looked at."

But Lisa's biggest challenge in the film was not the aggro but the physical intimacy that grows between Nicky and Chris as they fall for each other, despite the certain knowledge that any relationship will make life more difficult for both of them.

"The sex scene has a wonderful moment where I run my hands over his hands and kiss him, and we were in our trailer the night before and I was saying 'Oh God Mat, I'm really, really nervous about the hand scene because I hate my hands. I can't stand them.' And he turned round and said 'Look, we've all got hand baggage, OK?' "I wouldn't have got that from an able-bodied actor."

l Every Time You Look At Me, Wednesday, 9pm, BBC2