I recently impressed some journalists by having a banana for breakfast, while next to me Ken Livingstone tucked into bacon and baked beans. But the truth is that, if there's time in the morning, I love to indulge in a bacon sandwich. It's just that what with campaigning for the mayor of London recently, there's been very little time for eating.

I'd normally have coffee with brioche (with 100 per cent fat butter - I love it) for breakfast, but I ran the London marathon this month and I gave up caffeine because Seb Coe told me it was dehydrating. I had one day of caffeine hangover but now I'm fine. Since there's no morning coffee, I'm having smoothies instead, too - today's was cherry, banana, apple juice and frozen yoghurt, from a place that makes them from fresh fruit round the corner from the Liberal Democrat campaign offices. Even before I did the marathon I was pretty healthy though: I went to the gym or swimming three times a week.

I grew up in south London, but in the 1960s - well before there were so many different cuisines there. In our family you could tell what day of the week it was by what was for dinner: Sunday roast obviously, but on Mondays it was shepherd's pie, and pork chops on a Tuesday and so on. I didn't eat a Chinese meal until I was 20. My mother, who is 88 now, is still a great cook and I try and make it to her house in Sutton once a month at least for her Sunday roast. She does roast beef, Yorkshires, three kinds of vegetables and her speciality is lemon meringue pie.

When I joined the police force in 1976, I lived on McDonald's and cheese-and-pickle sandwiches. However, when I became a senior police officer at Scotland Yard I was incredibly lucky, because the cook in the senior police officers' dining room was a wonderful woman from Ghana - the room was always packed on Thursdays when she made curries with chicken, coconut and mango chutney.

I love to cook but I hardly manage to now - there's barely time to blow my nose, let alone cook properly. Last night I had a cannelloni ready meal - all that fat and pasta, wonderful. If I have time, I do fillet of beef with garlic, ginger and spring onions, and a sauce made with dry sherry and chicken stock and rice cooked with turmeric. My partner does really delicious teriyaki beef with green peppers. My taste veers towards Asian flavours - we went to Nobu last weekend, with his sister and her partner. That said, I do like a good steak, or the Wolseley in Piccadilly does a fantastic sole meunière, swimming in more of that lovely butter. Yum.

In the basket

Chicken and coconut curry

Many nutritionists might warn Brian off this dish on account of the saturated fat in the coconut milk . However, I've never found any compelling evidence that saturated fat is harmful to health.

Sole Meuniere

Always good to see fish in someone's basket, though for maximum health benefit I suggest he opts for oilier varieties on account of the disease-protective omega-3 fats they offer.

Bacon

I'm a big fan of meat but would generally encourage relatively controlled consumption of processed meats such as this: their consumption is linked with an increased risk of certain cancers including those of the stomach and colon.

Roast beef

Beef is a good source of zinc, B-vitamins and monounsaturated (heart-healthy) fat. Paired with a variety of vegetables, this is wholesome and nutritious.

Lemon meringue pie

Something this rich in refined sugar is unlikely to do much for Brian on a health level. However, it's not as if he eats it every day. Naughty, but nice.

Fruit smoothie with frozen yoghurt

Smoothies are generally a convenient way to get some fruit into the body. But if you then add sugary frozen yoghurt you will get a very carb-heavy snack.

Cannelloni ready meal

Ready meals, such as this one, may contain a little too much in the way of processed foods. However, there are now a few ready meals available that are based on quite unadulterated natural ingredients such as meat or fish with vegetables.

· London votes in the mayoral elections on 1 May 2008.