I am standing naked in a damp, tiled room in Paddington with two heavily built property developers from the East End of London. Both are charming and more than 15 stone. Their cheeks are suffused with a rosy boyish glow that instantly reminds me of paddling pools and sand castles. 'Come on,' says one, taking me gently by the forearm and leading me towards a grey plastic curtain that seems to have steam hammering to get out.

Inside, they can hear us coming. Quite suddenly, the curtain is whisked back and a tiny, corpulent, bald man emerges through the fog carrying what looks like an enormous yellow pantomime wig in one hand. 'This is Moishe,' says the man holding my wrist as he leads me into the steamy gloom. 'And now,' says Moishe, 'you are going to be schmeissed.'

''Schmeiss' is a Yiddish word meaning 'whip', and the practice of schmeissing was introduced to the East End by Jewish immigrants in the early part of this century. It involves a steam bath, a specially made raffia 'schmeissing besom' (the pantomime wig) and a lot of male bonding.

Ever since the Twenties, a select band of prosperous East Enders has trekked up to the majestic Edwardian halls of the Porchester Baths every Monday, Wednesday and Saturday to schmeiss each other for two or three hours in the heavy steam. They talk, drink tea and tell tall stories about schmeissing culture.

'There used to be a great hierarchy down here,' says Michael, a cuddly ex-public schoolboy of about 50, still sporting a fine pair of sleek rugby player's hips. 'The old guys who came here to have a bath used to bring their sons along to carry the buckets of cold water (used for dousing the schmeissee in between bouts of heavy pummelling). Then, if you stuck at it, you'd get to soap up the besom (twizzle it about in a big terracotta tub). And finally, when they got to the right sort of age, they'd give you a schmeiss - just at the end, if there was time. And you might not get another one for a year. When I started coming here in the Sixties, it took six months before anyone would say hello to me.'

Over all those years, the regular schmeissers formed into three separate groups, bathing once a week on Monday, Wednesday and Saturday respectively. Trevor, a professional poker player, is now a senior member of what he and the other regulars call the Monday Club.

'When I was a kid we didn't have a bath in the house,' he says. 'The people upstairs had one, but they used to keep coal in it. Everyone used to go out for a bath. And if you'd got a bit of dough, you'd come somewhere posh, like here.'

The Monday Club is a pretty cosmopolitan outfit. Ashem, an Iranian who first came to London in 1962, has been a regular Monday man ever since. 'For 30 years I never accepted a job that didn't give me a Monday off,' he says. 'I'm a schmeissing addict.'

I can understand the boys enjoying a bit of clubby repartee once or twice a week, but surely all this reverence for bath time is overblown? The schmeissers parry every question with a dead bat. 'Your body is like a car,' says Moishe, 'and a schmeiss is like being serviced.'

'Nothing in the world will make you more relaxed,' says Derek, the property developer, a self-confessed hypochondriac.

'It's been proved scientifically that it's all to do with sweat. Places like Georgia and China and stuff - they find people living to 160 and 170 years old. They've looked into all the food and everything and the only thing they could find is that all these people sweat a lot.' The others are too relaxed to disagree.

Mickey, a gnome-like octogenarian who makes his own mops by hand, sees things more spiritually. 'Years ago, if things were bad, my mother used to say to me: 'Go in the Turkish bath. You'll meet all your friends there. And you'll find the only difference is that one'll be rich, one'll be poor. One'll have a big schmuck, one'll have a little one'.'

''In a group of naked men, no one is looking for any advantage,' adds Ashem. 'They come here to forget everything and to relax.'

Four years ago there were more than 100 regular schmeissers, with schmucks of all shapes and sizes, bathing weekly in the Porchester Baths. Then the baths were privatised and the new owners banned schmeissing in an attempt to attract the yuppie market.

'It was becoming like a cult,' says Dorinda Berry, the spa manager. 'We didn't feel it was very social for people who were coming here for the first time and weren't educated about the schmeiss.' There was also talk of sex in the schmeissing room, which the schmeissers vigorously deny. 'If anyone can get his old bill up in that heat,' says Frank, a keen schmeisser and Soho security guard, 'I'll give him pounds 100.'

Either way, the old curtained beds and Edwardian wash-stands in the beautiful changing hall were torn out and replaced by plastic, Eldorado-style sun loungers and terse notices forbidding the vaguest hint of a besom. Eighty or so hard-core schmeissers left Porchester in protest and set up their own baths in Canning Town.

'Those people are gone forever,' says Moishe. 'There was a tradition from father to son to grandson in here - and you can't just tell people to stop something that has been going on for years.'

A tiny rump, however, addicted to the stately splendour of the Porchester Baths, remained to campaign for the return of their beloved bath-time hit. And eventually, Dorinda caved in. Now the die-hard Porchester regulars lounge about like victorious gladiators on her plastic chairs, drinking endless cups of tea, rubbing each other down with the raffia mop and telling tall tales.

At the end of a long and ludicrous story about a soldier with a bent penis, Trevor pauses for thought. 'The one consolation of age is that your control of ejaculation is so much better.'

'It always takes me one hour and 20 minutes,' says Moishe, patting his head with a towel. 'Twenty minutes to get ready, one minute to do the business and an hour to sleep afterwards.'

Beneath this kind of banter there lies a bedrock of old-fashioned sexual separatism that adds to the place's uncanny resemblance to a school dormitory.

''Men just don't relax with women,' says Derek. 'If men want to go out, they go out with men. If we had women here, we couldn't relax.'

Some of this chit-chat raises more than eyebrows among the image-conscious City kids - some of whom even wear swimming trunks - who come to Porchester for the newly installed saunas and Jacuzzis. 'Sometimes the set looks like Flipper the Dolphin,' says one regular. 'We keep out of their way and they keep out of ours.'

But the schmeissers are happy to bask in the glory of the sharp set that have been drawn in by matchless Dorinda and her marketing minions. 'Frank Bruno comes down here,' says Trevor. 'I've seen him.' Mike, a burly man glowing the colour of rhubarb from his schmeiss, adds wistfully: 'I used to be his masseur. I was the only one who could bend his legs.'

'We get all the celebrities here, you know,' chimes the tireless Moishe. 'Wayne Sleep, Omar Sharif, that band the Who.'

Down in the schmeissing room, I am led to a bench and laid out on my belly by eight muscular but gentle hands. The temperature is hot almost to the point of panic. Above me, out of sight, Derek starts to swing the schmeissing besom back and forth, with the sound of a single enormous flapping wing. With each wing-beat, a wave of heat is driven against my back. Then Moishe takes over, scraping the thing into my shoulders and pit-pattering it up and down my back.

Next Frank the security guard manages to do both of these things at the same time - and the effect is like being danced on by a tiny woman wearing an immense, oven- hot petticoat and sharp stiletto heels. They schmeiss me, they douse me, then they schmeiss me again. And, finally, they pick me up and carry me like a steaming tea bag to total immersion in an icy plunge.

I come round in the lounge room in a state of hyper-relaxation. Moishe presses a cup of tea into my hand. 'Mbiah,' I say, weakly. If I ever wake up, I tell myself resolutely, I'll come back here and beg them to take me on as an apprentice water-carrier.

(Photographs omitted)