I have often thought how nice it must have been to be a moneyed gentleman in the golden era of the St James's clubs. Overstuffed armchairs, comfort food, familiarity and peace: in my imagination, the concept is a bit like an upmarket Starbucks, without the hazelnut syrup and bleeping mobiles. Well, I have found something even better. Forget being a member of a club; the X factor that makes modern life perfect is to be a regular at London's May Fair Spa.

The May Fair Spa is just around the corner from St James's, in the Radisson Edwardian hotel near Berkeley Square. For two weeks, I was looked after by the adorable Liandi. (I became so attached to her that early in the second week, I looked in the mirror and realised I was subconsciously copying her hairstyle.) On my first visit, Liandi performed a diagnostic reflexology treatment and skin analysis, then an Indian head massage. On the basis of this, my programme for the fortnight was mapped out: three personal training sessions, two facials, two massages, a remineralising body wrap, and another reflexology treatment.

But the most luxurious part was being able to hang out in the spa. It is not difficult to find good treatments in London, but it is hard to find spas where the experience adds up to more than getting undressed, having a facial/massage, getting dressed again and coughing up. Here I was encouraged to arrive an hour before each treatment to take advantage of the sauna, steam room, and - for the brave - "plunge pool" shower, in which a bucket of icy water is emptied on your head. (What's that like? Who knows? Like I said, it's for the brave.) After treatments, you are led to heated marble loungers and served reviving herbal tea and sorbet.

Personal training was a revelation: I worked much, much harder than I ever would alone; an hour passed in a flash. (Knowing a facial or massage followed eased the pain.) By the end, I had rediscovered my motivation and had a whole new routine. Following Liandi's advice - her reflexology diagnosis suggested that my digestive system was overloaded, not surprising since I am legendarily greedy - I gave up wheat, and felt bouncier within a week. After microdermabrasion, oxygen treatment and vitamin-packed masks my skin glowed like never before; knots under my shoulder blades melted away under Liandi's hands.

When I opened the email offering me this assignment, it was in a Paris hotel room on the last day of a month of fashion shows. I was staring at my computer, bleary-eyed, eating minibar peanuts and drinking Coca-Cola in lieu of another missed dinner. Yes, I thought two weeks later, as I lay on a marble lounger, lingering over my final sorbet - yes, life has changed.

Did it work? It certainly de-stressed me. However, giving up the spa was stressful all over again.

Would you do it again? Yes, please.

Is it worth the money? Not a budget option, but surely money well spent.

What did you learn? Indulgence can be good for you rather than naughty.

· May Fair Spa and Health Club, 020-7915 2826, mayfairspa.com. Prices from £30 (lip-smoothing treatment) to £300 (full detox). Click here for reader offer.