It wasn't just the bombs. Even before Thursday I was 70:30 against traveling on the Tube. This may be because I live on the Northern Line, which must surely be London's worst - a new excuse for failure to provide trains echoing over the Tannoy every morning, and hideous, airless overcrowding in the carriages (though perhaps everyone thinks that about their own Tube line).

Or it may just be simple claustrophobia. The bombings decided me anyway - the monotone accounts of survivors, emerging with gashed faces and the eerily calm voices of people in shock to describe the horror of soot and fear they went through in those enclosed spaces deep underground. It will be a long time before I set foot on a Tube or bus again.

It's not that I want terrorists to succeed in disrupting London life. I'm planning to go on as I did before. I was happy to go back to work. And I've been in and out of the City and the West End and Westminster for the past week with no more than the same small flashes of anxiety I see on every other face - the fearful look at bags that don't seem to have owners; the shamefaced smiles a moment later. The only difference is that I'm going to do it by another form of transport.

So I've become a conviction cyclist. The bike that's been rusting gently against some railings near my office for most of the winter - ridden once or twice a week, but mostly abandoned while I nipped on to a Tube or bus or, on weak-willed days, into a taxi - has had more of a workout in the past few days than ever before.

And I'm not alone with my dirty little secret. For all the talk of Blitz spirit and London stoicism, thousands of other people are doing all they can to stay out of the Tube.

Since Thursday, the streets of the city have been packed with cyclists - to the point that, what with the sirens and traffic jams and outbreak of unexpected hot summer weather, central London has begun to look like one of those Asian cities where everyone cycles around in a haze in a haze of pollution, wearing vests and shorts.

Admittedly, there is a hard core of London cyclists who have been at it for years, but there are plenty of rank newcomers to the tough world of guerrilla biking. Those on the newest bicycles of all appear to be suffering qualms; an anxious-looking businessman in neatly pressed clothes, sighted on Monday morning in Islington worrying about whether to fold his jacket over his arm, or if the reflector band he's pinning to his chest will rumple his shirt; a mother wobbling down New North Road with three children of decreasing sizes, the smallest with stabilising wheels on the sides of his tiny bike, like a mummy duck with her ducklings heading off to school on the fringes of the City.

I was so intrigued about the appearance of the post-bombing cyclists that I asked a bike shop. "We've been selling bikes left, right, back and centre," answered a breathless Markus Blanshard, deputy manager of the Camden branch of Cycle Surgery, a chain with six branches in inner London. "There have been queues of customers coming in since Thursday saying 'I want something to commute on, rather than taking the Tube.' They're so desperate they'll take anything." On a normal Thursday afternoon, he added, the entire Cycle Surgery group turns over no more than £2,000. But last Thursday, a single outlet on the edge of the City sold £20,000 worth of cycles. "And it's been going on ever since."

Most of us fair-weather cyclists probably suspect that we'll be back on the Tube by the first nasty weather of October. The truth is that statistically it's far more dangerous to ride a bike than take the Tube, even with suicide bombers on the scene. But at least - on a bike, in the sun - you can enjoy the illusion that you're in control of your own destiny.

Slices of London: e-mail Urban Fox here