I suggested lunch, as one often does. Then, of course, I realized that this was extraordinarily tactless, to a woman who had vowed, publicly, to lose 18kg in 19 weeks.

But, far from being put out by my blunder, Alison Moyes welcomed lunch. We sat in Grozd, she enthusiastically dealing with a green salad ("No dressing, please") and soda water; while I, somewhat less enthusiastically, pacing her with my own (dressed) lettuce leaves and washing down the soda like it was due for a shortage any moment. But I now confess, as I hadn't to her at the time, that I did have intentions upon the chocolate shop, post-lunch en route back to the office.

I would be dishonest if I didn't also confess that at the British Embassy's Queen's Birthday Party, I did think to myself what a fine figure Alison was cutting these days, and wondered that I hadn't noticed before. It so happens that this was the point at which she decided that 70kg was just 18kg more than a girl could take. But why? There's a lot to be said for a woman who, as the Bengalis say, "has something there" - and nothing complimentary to be said for the pasty-faced, scraggy anorexics that many deluded teenage girls take as their role models.

Well, to be fair, Alison has no designs upon the latter. She wants to get back into her wardrobe - a little black velvet number in particular; and she wants her "blob" to become a "figure." Fair enough. She has gone public with these aims, invited sponsorship for each shed kilo, and will donate everything raised to the Bulgarian charity fund, run from the British Embassy where she works.

I wasn't surprised that she had gone about this in a very systematic way, taking medical advice about the optimum weight range for her build, and the right kind of balanced diet. This was changing eating habits forever, she said, not binge dieting. Once down to 52kg, she was going to stay there. No more chips, crisps, sweets, chocolate, fried food or popcorn - and alcohol down to three units a week. Now, now - isn't this taking things too far? Each meal is structurally organized to provide the right nutritional balance and to scare those kilos off - an average of one a week - though after the first flush, when the weaker-willed of her kilos ran away screaming, she now has to "work for it" and terrify the more recalcitrant ones with exercise and power walking.

You see, she's done it before. Before? Yes, in Fiji. So what went wrong, if turning a "figure" (her word) into a "fine figure" (mine) can be described as wrong? Well, moving to the UK and living off fish and chips while decorating a house for a year. Fish and chips - the slippery slope. Her weakness.

Mind you, Fiji seems the wrong kind of place to lose weight seriously. You will remember the gloriously "blobby" Queen of Tonga who took part in Queen Elizabeth's coronation procession. "Who is that in the carriage with the Queen of Tonga?" an onlooker asked the late Noel Coward. "Her lunch," he replied.

So what's different this time? Well, peer pressure; the thought of public failure; her husband Dave's support; and the thought of that little black velvet number versus the cost of a new wardrobe.

I left lunch absolutely impressed by Alison's determination and common sense. As for changing eating habits forever - well, I hope she gets pleasure out of her new regime, I'm not convinced that I could. Meanwhile, you can still support her and help the children's charities which the Embassy raises money for.

Contact Alison at the British Embassy, but hurry before it's too late - D-Day is October 31. There'll be unlimited lettuce leaves and soda water to mark the day. Though she's no evangelist, and I'm sure will condone beer, chips and chocolate for the celebrations of the unreconstructed.