I have a lovely GP, a splendid man, but when I told him about my migraines he said, "What do you expect?" I translated this into, "There's not a lot you can do, with the amount of stress in your life." I'll do six shows with no time between them without thinking. Then I'll get three days off and I'll suddenly realise I've had a diabolical week - which is when the migraines strike. It's as though I've given myself permission to have one because I've got some free time.

I've never missed a show because Doctor Footlights steps in - in other words, the sheer adrenalin rush you get when you have to perform in front of 500 people. A humdinger of a migraine can drop by 50 per cent when I'm on stage because my mind is concentrating elsewhere. You'd be amazed at how much pain you can stand when you have this huge focus. But after the show it kicks in with a vengeance.

About twice a year I get a complete thumper. I'll be throwing up and lying in a darkened room for weeks. But usually, about once a fortnight, I get the kind of headache that feels like a bad hangover - and I don't even drink.

The only pain-killer that will touch it is Migraleve, which I buy in bulk. I secrete little capsules everywhere. They're in the car, my make- up bag, my briefcase, there's always a couple in my handbag and beside my bed.

I can't remember when I had my first migraine, I've only been conscious of them in adult life. But then, I have a terrible memory for detail. I have a stressful life but it's better than packing shelves in Safeway. Although, at least you could phone in sick and somebody else would do your job. In my business you have to be there - there are no excuses. But my migraines are not a life-destroying situation and don't affect my every waking moment. They haven't stopped me achieving my ambitions.

I know they say that cutting out certain foods can help - it's always oranges or chocolate or something. But for me there doesn't seem to be a correlation. I haven't had an orange for three weeks, and I've been trying to lose weight, so I can't remember the last time I had a piece of chocolate, but I can still feel one coming on. If my migraines are diet- related then it's something really bizarre. I thought the cause might be eye-strain, so I got reading glasses, but it hasn't knocked the pains on the head.

The worst migraine I ever had was three years ago when I was moving and was making a 40 Minutes documentary with the BBC. Everybody advised me not to do it and I was receiving major flack from the magic community. I was under a huge amount of pressure at the time. It's not a particularly nice feeling, somebody unscrewing the top of your head.

Interview by Cayte Williams