Forget Jeremy Clarkson’s rants — we need a 20mph speed limit

The move to impose a 20mph speed limit, accompanied by heavy fines for speeding and dangerous driving, was bitterly opposed.

But its detractors were forced to admit that they could not stand in the way of progress: so it was, in 1903, that drivers got their way and the speed limit ratcheted up again from its previous 14mph.

Now my borough, Southwark, is heading in the other direction. It aims to make 20mph the default speed limit on the borough's roads (not the arterial routes controlled by Transport for London) by 2013. My Herne Hill neighbourhood is set to slow down shortly. Islington last year announced plans for a similar borough-wide limit. Other cities are moving in the same direction.

The reaction of some motorists has been predictable. Internet forums are full of rants against "enforced Left-wing extremism". Jeremy Clarkson suggested a few months ago that most drivers could brake to 20mph if a drunk steps out from behind a bus, and that "especially if he is really drunk and therefore all flobbery", the pedestrian will emerge unscathed.

With that sort of standard of debate, they're not going to get far. One study last year concluded that 20mph limits reduce road injuries by more than 40 per cent. The reduction in injuries to child pedestrians was particularly striking. Researchers estimated that a capital-wide 20mph limit outside of arterial routes would prevent almost 900 casualties a year.

In truth, a lower limit will make minimal difference to most journey times. It might even make them smoother: last December the road safety minister announced that lower speed limits need not necessarily be enforced with speed bumps. Those annoy me as much as any other driver.

And the problem with speed limits has always been enforcement. In January 1896 the hapless Walter Arnold, of East Peckham, Kent, became the first British driver ever successfully prosecuted for speeding, racing along at 8mph in defiance of the prevailing 2mph urban speed limit.

He was caught only because a policeman happened to be able to give chase on his bicycle. But for many years now, you've had as much chance in south London of being stopped by an actual policeman for speeding as you have of being cut up by Jeremy Clarkson on his bicycle.

Enforcement will change, though, with the new digital speed cameras which can take cars' pictures on entering and leaving a given area; networked, they will work out its average speed. Southwark will be trialling some of them starting later this year.

I feel distinctly uncomfortable at the prospect of yet more cameras gazing down on our streets — especially highly sophisticated ones. Authorities from the police to local councils always pooh-pooh the idea such surveillance could be misused — and the next thing you know, they're using powers designed to combat suicide bombers to clobber someone for dropping a fag butt.

In the end, though, it is my children that make me favour a 20mph limit. It's sad to have to subject responsible drivers to a new layer of electronic control.

But if the new limits keep people such as the guy who roared past my six-year-old son recently, missing him by six inches, off the roads, then the odd extra minute dawdling on London streets will be a price worth paying.