IT IS 8 pm on a freezing night in Cambridge. Under a crescent moon and five floodlights, the Varsity rugby team is coming to the end of a training session. The field is strewn with shiny puddles and pockmarked by the studs from their hefty boots. Mud clings clammily to feet, clothes and the ball, slowing movement and making running harder, falling dirtier.

None of this modifies their energy or enthusiasm. An injured team member (broken collar-bone, arm in sling), who has come to watch the practice from the sidelines, hollers: 'Well done, Jackie] Run] Run] That's good]' At the far end of the field, a group huddles round the scrummaging machine, all but invisible in the darkness.

The 15-strong team and five reserves do a two-hour training session two nights a week, a sprinting session on Tuesday mornings and kicking practice on Fridays. The forwards do weight training in the gym in addition to this and they have a match every Sunday. But this Sunday is the big event of their year - the Cambridge-Oxford Varsity Match. These women will probably never be so fit in their lives again.

Women? Of course they're women. Rugby is one of the fastest-growing women's sports in Britain today.

From the darkness of the field comes the voice of Jim Ashworth, their coach, as they gather round for instructions. 'Look for those quick ones when you come out the back] You've probably been through most of the combinations, but when they're not ready it's the easiest way to score a try.'

The striped shirts and tracksuit bottoms pound off in a new direction. The ball arches through the air and lands with a dull thud and a splash. 'Let's go girls, let's go - I'm watching - come on, good effort] Really work it - why are you jogging?' They're hurtling down the field like stampeding buffaloes: what more does he expect? Breath clouds the air and one or two people are coughing, but as they thunder past I can't hear anyone panting.

In the face of such peak condition injuries are an irritation, not a deterrent. The sidelined team member, Emma Jones, who is 20 and plays centre, is philosophical about her sprained ankle. 'Rugger is a contact sport and you have to accept that risk,' she says.

Emma is small, with long blonde hair, and is reading veterinary medicine at Newnham. Now in her second year, she played in last year's Varsity Match. 'For most of these girls it's new when they get to university. I think they'd have great trouble introducing rugby in schools, judging by my mother's reaction when I started.'

Across the far side of the field a line of poplars is silhouetted on the horizon and beyond them shine the lights of houses. The tall goalposts gleam white against the night sky. Out on the pitch the practice is over and the team is 'warming down'. This consists of doing 20 press-ups in time to the coach's metronome counting ('17, 18, 19, 20] Now on you go]').

They jog 50 yards and sprint 50 yards; then do 20 fast sit-ups, run again; then 20 squat-jumps, more running; and finally 20 star-jumps. They're back in the corner they started from and - I can hardly believe my eyes - they're going to do the whole routine again. 'OK, for the next 25 yards really let it go]' shouts Jim. 'Move it]'

Twenty or so pairs of rugby boots squelch thickly, stickily towards the clubhouse. The women look exhilarated rather than tired, skin and eyes shining through the splashes of mud. Sitting on the steps while they unlace their boots and prepare to cycle back, I enquire feebly if the training session wasn't very exhausting. 'You can run up to 10 kilometres in a game, but when the adrenalin's going and you're fired up you don't even notice . . . till you take your shirt off after the match and see all the bruises from collisions and falls.'

Does the game alter their shape? 'Your shoulders grow - feel my neck]' says someone, and I gingerly palpate a size 16 column packed with muscle. 'Your stomach tends to flatten and shrink. You lose round the waist and gain on the shoulders and thighs. It's so tiring that you tend to eat more, carbo-loading with lots of pasta.

'But, like any sport, it makes you feel better, and when you go home at the end of term you find you can't sleep because you haven't worked out your body. It's a wonderful way of getting rid of stress, too.'

We make our way to Caroline Scott's room in St John's College. The walls are covered with the usual sort of posters - Axl Rose and various model bodies, male and female. There are cheerful mugs to drink out of, a striped rug on the floor and a large vase of white lilies on the side. A pair of goldfish swim disconsolately in a small, cloudy tank.

I ask Jim the coach whether the women (although I steadfastly call them 'women' they, and he, all refer to them as 'girls') train and play differently from men. 'They can be just as aggressive as the lads,' he replies, 'but they're brought up differently. It's more a question of gender than weight. And girls don't tend to have the same ball skills.' Nobody sniggers.

Veronique Robinson, from Jesus, who is reading modern languages, came back early from her year abroad in Italy (where she played with the Milan team) specially for the Varsity Match.

'The thing about rugby is that most of us have come to Cambridge without ever having touched a rugby ball before and you have to learn to spin the ball - pass it backwards - in the first year or so, whereas boys have been doing it since they were at school.'

Have they noticed mental or psychological changes in themselves as a result of playing an aggressive sport? They all nod. 'Yeah.' And Veronique - whom the others call Vezza - says: 'You feel responsibility for the other players. You don't let someone go off on their own into a pack of the opposition.' Jo Kamerling adds: 'You support each other emotionally off the pitch as well. So there's that, as well as channelling all the violence . . .'

The others chorus laughingly: 'Violence? Freudian slip, Jo] The word's aggression]' 'Well, whatever - it's setting yourself a job and getting it done. You want that ball and you want to score,' Jo says. 'And then you can get on better with the rest of your life.'

Does it affect their relationships with men? Stephanie Gill says: 'When I first started it was, 'What the hell are you doing playing rugby? How dare you?' ' and Jo adds: 'They sometimes say, 'What are you trying to prove?' '

Clare Newall, one of three on the team reading engineering, says: 'My boyfriend hasn't come to watch me play yet, though he's coming to the Varsity Match. But he's actually very proud of me because I'm going to get a half Blue, so he's quite chuffed.'

What about work? They play what used to be thought of as a male game; so do they also tend to read 'male' subjects? Vezza says: 'Yes, but not by a significant majority. Besides engineers and scientists, we also have a lawyer, a historian, a vet, and two linguists in the team.' Is their work affected by the time needed for training? 'I couldn't work without having done exercise - I'd go mad,' says Jo.

Do they go drinking afterwards, like male rugby players? Fingers are pointed at a couple of offenders. 'We go out and socialise,' says Lisa Norcross, the captain: a second-year engineer. 'But it's not like the men who go out and sing and take their clothes off.' Much boisterous laughter at this idea. 'But the point is,' someone says, 'you can drink orange juice and no one minds. Girls don't need drink to make them feel close and let their hair down.'

They've only beaten Oxford once in six years, but this Sunday they're determined to win. Cambridge are in the second division and Oxford in the first, but Cambridge have at least two players better than anyone Oxford can field, they believe. Hopes are high.

'It won't make any difference whether we win or lose,' says Lisa, the captain. 'Everybody will be really relieved after it's over because there's been such a big build-up. You want to play your best to show your friends you're not wasting your time.'

And afterwards? How will they celebrate? 'We're having dinner in one of the colleges with the Oxford team and all our coaches, so we'll have a really good time.' And no filthy songs? They laugh, healthy, hearty and, somehow, touchingly innocent - far too innocent for filthy songs . . .

The Oxford v Cambridge women's rugby Varsity Match is played next Sunday, 7 March, at the Cambridge city rugby ground, Grantchester Road. Entrance is free.

Reggie Nadelson is on holiday.

(Photograph omitted)