Don't be shy, Boris, just tighten your chinstrap

Not according to our cycling Mayor, Boris Johnson, who this week wrote in defence of his right to go bareheaded. He set up the great cycling-helmet debate as a dilemma between "safety and liberty" but concluded that "we should be able, in our muddled way, to make up our own minds". So liberty beats safety.

I'm not so sure it should. Boris is keen to quadruple the number of bicycles on London's roads. Yet ask a refusenik why they won't cycle and they'll usually cite safety worries as their biggest obstacle.

They're quite right to worry because riding in London takes nerves of steel and we need trustworthy advice on how to stay in one piece. But many bike enthusiasts are still prone to raise studies that show protective headgear is futile.

I have a problem with these findings - they don't pass the commonsense test. How can it be better to hit the road without the protection of a helmet? To paraphrase a surgeon friend who works in A&E - you show me a cyclist with the wind in his hair and I'll show you a grieving mother.

The BMA is so convinced of the benefits that it's calling for helmetwearing to be compulsory.

My own experience tells me it's safer to buckle up. When one stressed commuter strode in front of me on a Bloomsbury cycle lane I slammed on the brakes too late and butted him squarely in the head. He walked off with a visible bump growing but I got away with a grazed knuckle. Another time, a gaggle of drunk girls zigzagged across a Soho street, causing me to swerve and smash my head on the kerb. The helmet was all that stood between me and concussion - or worse.

So why the reluctance to lay down the law on helmets? Perhaps it's because cycling still occupies a legal grey area where proper laws are resisted and debated. It's illegal to go through a red light but we cyclists often do. Bikes can't be sold without a bell, but who uses it? Lights are mandatory, yet I often see unlit riders darting past in the gloom.

The resistance of cyclists to regulation reminds me of the huge public opposition to seatbelt-wearing in the Seventies. Now we buckle up without a second thought, and of course it's safer.

I do struggle to don my helmet every day, especially when I want to keep my hair nice. But in the three years since I started cycling in London, it's obvious that the majority of us have overcome our reluctance to them.

Boris should get over his helmet hang-up. He's no longer just a guy who cycles to work in London, he's a bicycling ambassador. I hope he gets as many Londoners on their bikes as he wants to. But do it safely, Boris - or more cyclists will translate into higher accident statistics. It's high time we tightened our chinstraps.