Last week, Donna Maddock of Mold, North Wales, was caught applying make-up with both hands while driving a car at 32mph. A serious offence, you might think; certainly one punishable by law. But Ms Maddock managed to make the whole incident into a bit of a joke, cleverly turning it from reckless endangerment into a bit of silliness. How? By describing it, presumably with a little giggle, as "What I would call one of my blonde moments".

Not so fast, Donna. We've got your number. You are playing classic blonde strategy, and this is how it goes. You are in trouble. So you divert people's attention from your faults (dangerous driving) and towards your assets (nice blonde hair, a sense of humour). It ensured that her misdemeanour was filed, so to speak, not under "Crime" but under "Trivia". It meant the incident was reported not in the "Legal Reports" section of the newspaper but in the "Lifestyle" pages, under the sympathetic headline "I wanted to look my best" - all presumably of some comfort to Ms Maddock, who covets a career in modelling and has appeared as "Miss January" in a "Chav Calendar". For her, a mistake has turned into a boon: blonde alchemy.

I point out Ms Maddock's technique in the spirit not of disapproval but of goodwill. In fact, I regularly spend several hours in a salon just so that I can play the same game myself. You never know when you are going to have to excuse yourself from the inexcusable, so it's as well to have the hair ready in advance. You don't need to say anything corny - the "speak slowly, I'm blonde" jokes shouldn't be trundled out except in dire emergencies - but just by having a golden head of hair you can claim an innate advantage, due to its association with halos, angels, children (remember how many of us start out blonde and get darker with time) and countless film stars. I find hydrogen peroxide judiciously applied works all kind of voodoo. It seems to make you look like the kind of person who has simply mislaid their tube ticket. It seems to make you more likely to catch the bus. And, according to the psychiatrist John McGeorge, "a woman has a much better chance than a man of acquittal on a murder charge. If she happens to have fair hair her chances rise by about 45 per cent". I am glad to say I have never put this theory to the test.

Playing up to the dizzy stereotype is a profitable game. Chantelle Houghton, the non-celebrity who won Celebrity Big Brother, is permanently having a blonde moment. She showed how sending yourself up makes you look self-aware and self-deprecating. And she also showed how non-threatening it can be, by saying of her co-contestant George Galloway, "He's a male chauvinist pig" - and immediately adding, with a toss of her yellow extensions, "whatever that means!" She knew perfectly well what it meant, of course. She was simply using her dumb blonde persona to defuse this potentially aggressive statement. Rather artful blonde diplomacy, wouldn't you say?

However, the "don't blame me, I'm blonde" line has been occurring with alarming frequency recently. Only last month, a female driver in the Manchester area used it to explain why she got into her car and reversed it into a lake. Blaming your hair colour for the stupid things you do is so audacious that it makes people laugh. If it doesn't take people at least a little bit by surprise, the charm will no longer work. So perhaps, to keep the conceit fresh, we women should hand it over to men. I can think of a few candidates. Boris Johnson. David Beckham. But then again, they might not be skilful enough at using it. You have to be rather clever, you see.