Like most women my age I'm bothered by the business of ageing; six months from 60 my thoughts turn inevitably towards the advancing years. Of course I know it is impossible, and I'm not so trivial as to think it really matters. The sensible side knows that to be obsessed with ageing is pathetic: all the cosmetics in the world won't hold back the Grim Reaper, as the medieval moralists loved to point out.

Still, even the slimmest possibility of being able to look ten years younger in a single day calls like a siren. It was the outlandish claim I read from a new wellbeing centre in Kensington, West London. The brainchild of Carolan Brown, former personal trainer to the late Diana, Princess of Wales, the Soma Centre has devised a new day programme that offers to "empower and educate you to look and feel over 80,000 hours young in mind, body and spirit". All that in just one day.

Naturally, I felt sceptical, especially when I looked at the programme. It was a mixture of consultation and therapy. A facial is always enjoyable, but how was talking to a nutritionist going to help? She might recommend vitamins but she wasn't going to put them on my face. Surely the chief benefit would be taking time out of my schedule. For just when I should be taking more care of myself, I've become a workaholic.

Brown's dream was to offer a programme "to initiate the anti-ageing process from the inside out", since becoming truly aware of what you eat and how you stand is just as important as what you put on your face. So the nutritionist Petrina Gathercole, cross-examines me about my eating habits and - ouch! - how much wine I drink.

She explains that people see her because they want to lose weight, but she has to assess how the whole system is working. She tells me I can help my asthma through diet (red meat not more than once a week; cutting out cheese) and how eating more fish, seeds, pulses and a grain called quinoa will help me at this time of life. Discovering that I snatch only a yoghurt for breakfast, she suggests that I make my own muesli. "No way; I'm just not going to make time!" I retort, but then feel that I've disappointed her. Gathercole is making me focus on what I put into my body.

Gloomily resolving to cut down on wine, I move to my next consultant. Tom Bradley, a phsyiotherapist, is young and handsome, so I'm quite happy for him to check my posture. He offers the painful truth that "once over the age of 30 you're physiologically and biologically old", which is why it's important to maintain flexibility. "Think of how an old lady walks and don't do it! Think of how a catwalk model moves, all straight and swishy, and aim for that," he says. He points out the mistakes in my posture and gives useful tips; for example, someone hunched over a computer all day should make a habit of taking up perfect posture, pulling up through the spine, before answering the phone.

Next is a Pilates class with Brown herself. She's tall and lithe, with an easy, no-nonsense "big sister" air. "You can't put youth on to your skin," she says, "it has to come from within because if you feel good it shows on your face." Putting me through Pilates exercises, she is slightly horrified at my lack of flexibility, and so am I. Brown says that not enough people are prepared to invest in their health in the same way as they might buy an expensive handbag. She believes that the "core stability" achieved by Pilates does more than keep people supple and help with back problems. She is passionate about exercise as a way of relaxing and of easing depression.

Food, posture, flexibility...and at last the two beauty treatments. One hour will be taken up by a slimming and detoxifying body treatment using algae harvested in the North Sea. I feel like a joint being prepared for the oven: first the thick marinade. then a generous sprinkling of marine salt and a chilly spray of oil, then wrapped up in plastic film and a thermal blanket and left to "cook" for 15 minutes. The final salty massage is vigorous. When I pull my track suit on again my skin feels soft, even ten years younger. I fall asleep during the superb facial, drifting back into consciousness as more cooling unguents are applied to my face.

My naked features are now subjected to the scrutiny of a man who divides his time between Paris and London, with a list of starry clients in both places. Brown has added a half-hour consultation with the well-known French cosmetic surgeon Dr Jules-Jacques Nabet to the anti-ageing day because she's realistic. All the Pilates in the world isn't going to stop many women angsting about their wrinkles.

In a thick French accent Dr Nabet starts with his usual question: "'Ow can I 'elp you?", but instead of launching into the journalist's queries I'd intended, I tell him I hate how everything is heading downwards. He asks me about Botox and "filler" for the lines from nose to mouth, and I explain that I once had both about four years ago, to write about them. "'Av you ze time?" he says, and I'm thinking "what the hell". So we do a bit of Botox right there, although it wasn't on the programme.

Later I asked my boyfriend if I looked ten years younger. He appeared rather worried (wanting to get it right), but sweetly said: "You always look lovely to me." It was the best reply, as well as the only sensible one because of course you can't look younger in a day. But it is certainly possible -even when the three score is looming -to shift the way you think. We celebrated that with a glass of champagne.

Three months on, the change has happened. I'm making my own muesli, working out with a personal trainer, standing tall, and drinking about a quarter my normal amount. I feel and look much better.

In brief

USP Their claim of even the slimmest possibility of being able to look ten years younger in a single day calls like a siren.

AMBIENCE Clean and simple. What facilities? Just treatment rooms.

EXPERIENCE Fabulous; the best facial I've had. The therapist had magic fingers. It was a mixture of consultation, with a nutritionist and physiotherapist, therapy and Pilates with Carolan Brown, the former personal trainer to the late Diana, Princess of Wales.The one hour slimming and detoxifying body treatment using algae harvested in the North Sea actually made my skin feel ten years younger.

FOOD You go to the hotel for food.

IN CROWD I didn't see anyone else there.

WALLET WATCH The day costs from £400, with anti-ageing work, such as Botox, costing extra.

NEED TO KNOW The Soma Centre, Royal Garden Hotel, London W8 (020-7937 8000; www.royalgardenhotel.co.uk)

Bel Mooney answers your problems in times2 on Wednesdays; bel.mooney@thetimes.co.uk

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