This must be every metrosexual's worst nightmare. Here I am at a fashionable spa, naked as the day I was born, covered head to toe in a verdant goo known as spirulina - and the water has stopped working.

I can't wash it off. Spa attendants and beauticians shuffle around anxiously. I will remain coated in this stuff for ever, a lurid green merman in a state of perpetual detoxification. Perhaps I will become so detoxified there will be nothing of me left?

Before you send the newspaper windmilling across the Tube carriage, harumphing that any man who has a spirulina wrap deserves this indignity, I should point out that I was at the spa by accident. My fiancee came by some complimentary his 'n' hers treatments and I decided to offer up my body this once, in the spirit of research. I'm told these places are all the rage in our capital.

Before we began our treatments, we were given questionnaires to fill in to the gentle strains of an indoor waterfall. Do I have a regular skincare routine? Occasional showers. Which brand of skin product do I use? Thames Water.

Then we separated. I was to strip off and undergo a vigorous exfoliating sea-salt scrub; a full-body moisturise; and the aforementioned daubing in spirulina, which may sound like a venereal disease, or possibly an evil ballerina, but is in fact a kind of sea algae renowned for its restorative properties.

This weed would rid me of all impurities, including, it is hoped, any impure thoughts towards the obliging young slip of a girl who was slathering the stuff on my naked body. My fiancée was in the adjacent room, having the same done on her by, presumably, a well-hung and randy young hunk.

Thus coated, I was cocooned in a sort of surrogate womb known as a flotation tank. Twenty minutes of this were apparently equivalent to four hours' sleep. It was after this that things started to go wrong, as I attempted to shower the green stuff off and found no water forthcoming. My girl was visibly panicked but dealt with it impeccably, merely returning me to the flotation tank for a further 40 minutes as the spa technicians paid the water bill and H2O was restored.

What ran through my mind in that cocoon?

Hazy childhood memories. Disconsolate feelings of loneliness. A blissful kind of panic. Go to a hammam in an Arab country and such cleansing routines are performed communally and vigorously; in London, those who can afford it are locked away alone and quiet, with only their thoughts for company. Then again, I suppose if you are willing to pay for this kind of wheeze, you can't have many thoughts in the first place.