I began night walking not as a cure for sleeplessness, but because a year of reading nothing but Dickens had given me the idea that I wanted to see London as he had seen it. No visions of Horsemonger Lane haunt me and I rarely go out once in bed, but I have got into the habit of walking home at night from wherever I happen to be. If it is King's Cross, I dodge down Warren Street to escape the Euston Road and then through the streets of Harley Street and Marylebone with their townhouse doctors' surgeries and French boutiques. Beyond that are the garden squares — Manchester, Portman, Connaught and Norfolk — and home to Bayswater. 

Or up from Bermondsey after dinner, with a cup of weak milky tea in a Styrofoam cup from a hole-in-the-wall café at London Bridge to keep out the cold on the river. At Borough Market, late in the evening, the stallholders man great oiled hotplates of paella, risotto or pilaff, scraping and turning the last of the rice to stop it sticking. Around the replica of the Golden Hinde and Tate Modern, along the South Bank, over Waterloo Bridge and up the Strand. At Charing Cross, Trafalgar Square and Piccadilly Circus there are dog-legs and detours to avoid the crowds. Leicester Square on a Saturday night is a purgatory of short skirts, fake tan and hair gel. Then up Bond Street, crossing the road back and forth to get the best of the shop windows.

Oxford Street, intolerable by day, is a pleasure with its broad pavements to yourself. The rickshaw drivers sweat up and down the main drag, playing at Ben Hur and blaring Bangla music from their speakers while the miniskirts whoop encouragement from the back seat. The hot pie and potato men of Dickens's walks have been replaced by the man offering Belgian waffles with aerosol cream and the £1-a-slice pizza man. At Marble Arch, home is within reach, just the last stretch along the top of the park. A passageway cut through the wall of Hyde Park Gardens Mews — too narrow for two people to pass comfortably — takes me almost to the doorstep.

The walk I do most often is the one from work. My office hours are late enough that except for a few glorious weeks in the summer when the days are at their longest, I walk back in the dark. 

Turning off Kensington High Street, the temperature drops by several degrees. Without the heat of the buses and shops — and in the shade of an avenue of plane trees all day — Kensington Palace Gardens is cool even on the hottest, stuffiest nights.

It is poorly lit. The street lamps, among the last Victorian gaslights in London, are often out. You don't notice the Eastern Europeans guarding their respective embassies until you are near enough to hear the chatter of their earpieces. The presence of these heavies and the armed police around the Israeli embassy has done little to discourage the foxes. There are dozens of them to be seen each night, tripping in and out of the railings of Kensington Palace and crossing the borders between ambassadors' residences. 

There are less welcome creatures to be found when you reach Bayswater Road. After lessons finish at the language schools of Moscow Road, homesick Chinese students buy slimy pots of duck, rice and beansprouts from the takeaways on Queensway. They eat them leaning against the Bayswater Road railings and drop the remains through into the park where fat, indulged rats run along the gully between the railings and flowerbeds. You never see them in daylight.