My working method as an author is that I write in the mornings and then in the afternoon I wander, in a bit of a daze, around London. Generally I go north to Camden Town and Hampstead Heath or east through Shoreditch and Hackney. Sometimes I'll take a bus to somewhere alien like Canary Wharf and then walk back to my base in Bloomsbury, like a Chindit in Burma dropped behind enemy lines.
Even when I'm abroad in a foreign city I try to go for a stroll. The first time I was in Los Angeles – the most walker-unfriendly city in the world – late at night after we'd checked into the Chateau Marmont, my wife and I went for a wander along Sunset Boulevard. Ahead of us on the pavement there was a single person. "I bet he's British" my wife said. And indeed when we caught up with him it turned out to be Billy Bragg. On another occasion in the same city I walked along the straight, empty boulevards in the blazing heat, the only pedestrian for a hundred miles, only to bump into the actor Roger Lloyd-Pack, whom I'd been dodging all over London to avoid doing a charity benefit.
For me, walking literally puts you at the same level as everyone else. I find it a humbling, revelatory and sometimes frightening experience. There is a theory that people in the suburbs who drive everywhere are more stuck in their attitudes because they never encounter anybody who disagrees with them. Locked in your car, the radio tuned to a station that confirms your opinions, no divergent voices filter through the metal and glass. If you walk, particularly through a city centre, you constantly encounter different languages, opinions and ways of seeing. After all, the first thing any despot or egotistical rock star does when they attain fame or power is to stop walking: you can't imagine Robert Mugabe or Bono going for a stroll round the neighbourhood, popping into a shop to buy some wine gums.
There are some authors for whom walking is a central part of their process. Will Self and Ian Sinclair both write eloquently about the journeys they take on foot and – because his office is in my street – Peter Aykroyd toddles past the window in which I sit to write every day, though in his case he's only going to the corner shop to buy a minuscule container of milk and a tiny loaf. Still, I'm sure he gets a lot out of it.
The act of walking itself can be, if you tread with your eyes and brain open, fantastic for the imagination. Charles Dickens, too, lived in my street and he would walk for hours, through the law courts and the rookeries, seeking and finding inspiration for his fiction. The philosopher Immanuel Kant never left Königsberg, the city where he was born, but he would walk continually, describing huge circles around the town as he contrived his theories; while Jean-Jacques Rousseau was so devoted to walking as a source of inspiration that he wrote a book broken into 10 walks, Reveries of the Solitary Walker, in which the great philosopher attempted to recall the dreamy hikes he took and the thoughts he had while taking them.
If you don't walk to exercise the imagination then you should at least walk to exercise the body. Apart from the benefits to the heart, lungs and increased bone density, the latest research suggests that men who walk for an hour to an hour and a half a day are two-thirds less likely to get prostate cancer, though they are 90% more likely to get into an argument with a cycle courier.
• Alexei Sayle's latest novella, Mister Roberts, is published by Sceptre (£7.99)
