The skinny blonde in the tight grey leggings giggled nervously as the large ex-oarsman thumped her back, as if he were trying to dislodge some trapped food. 'I find all this a bit disconcerting,' she choked, pulling her sweatshirt down. 'But I suppose it's all about bringing down barriers, isn't it?'
Lydia was leading a Qi-netics class, a new form of exercise that combines the elements of t'ai chi with dance and aerobics. Originally from Singapore, Lydia has spent the past 15 years doing shiatsu massage and therapeutic healing.
'I got so fed up with healing people and them doing nothing for themselves,' she said as she ticked latecomers off her list. 'I wanted an alternative to aerobics. I wanted people to enjoy their bodies and exercise in a more fun way as well as channelling the Qi to create a meditative appeal.'
Lydia, who also gives lessons in Hampstead and Covent Garden, believes Qi-netics meets a growing need. 'I have more and more young people with high-pressure jobs coming to my classes,' she said. 'They just don't know how to relax or switch off and that's what I hope I can do for them.'
The lesson began with a series of stretching and breathing techniques. The class of about 35 men and women stood in two circles, inhaling and reaching towards the beamed ceiling, exhaling and looking through a small triangle created by placing their fingertips together. 'Relax and feel the Qi moving around your body,' urged Lydia. Everyone stared into the centre, except the middle-aged brunette with the safe-sex T-shirt, who was finding it hard to keep up. Arms flapping in the air like a young bird, she elbowed the tall hippie in the saggy track-suit bottoms. He was too relaxed to notice.
After the warm-up came the tribal dancing. As ethnic tunes filled the dimly lit hall, the participants were urged to express themselves. Snaking around the room to Middle Eastern chants, they wove in and out, touching various parts of other people's bodies. 'When someone touches you,' explained Lydia, 'you have to move that part in a circular motion.' This provoked enthusiastic yelps from a couple of lads with fledgling dreadlocks who minced around the room cuffing people on the buttocks.
The husband-and-wife team in the round spectacles, who had arrived late, found all this rather disconcerting and corkscrewed quietly in the corner. The other members of the group, including the woman in the safe-sex T-shirt, stomped and jumped, hurling themselves into the air and rolling on the floor.
Suddenly a woman from a yoga class downstairs burst in. She stood with her hands on her hips, her grey perm shaking with anger. 'I tell you about the noise every week and you don't listen] We can't even hear ourselves meditate,' she complained.
Quietly into pairs once more, and back-to-back writhing. The ex-oarsman grabbed an attractive computer programming student. Together they moved their hips in circles. 'This is great,' he said. 'But can't we do it front- to-front?' The rest of the class laughed, and the student blushed. She did not partner him again.
Then came the choreographed routine. Once more to tribal beats the class moved the length of the room in a complex set of steps derived from self-defence moves. 'If someone were to go for your crotch,' said Lydia, 'twist and shove your hand between your legs, like so, and they will never get you.'
The dreadlocked pair, although excellent at freestyle, found this regimented discipline more difficult and stood confused at the front of the class. The computer programming student, in contrast, found it a breeze and, twisting and chopping the air, she led the class.
After some meditation and breathing exercises - during which some people fell asleep - the class finished. The pupils hung around putting their socks on. 'I feel so much better,' said the dark-haired woman who worked for the BBC. 'It's the only hour of the week I don't think about work.' The woman in the safe-sex T-shirt agreed. 'It's such an escape.' The computer programming student was more expansive: 'I'm definitely joining the course, buying the tapes and the T-shirt.' The skinny blonde added: 'I feel sensually enhanced. Not only relaxed but buzzed, and quite sexy, actually.'
'The Taming of Eagles: Exploring the New Russia', by Imogen Edwards-Jones, is published on Thursday by Weidenfeld & Nicolson at pounds 17.99.