Earlier today I was proceeding, at an orderly pace, in a southwesterly direction down the A3.

It was a very bright day, and as I came under the Tibbets Corner underpass I spotted a policewoman leaning over the barrier of the slip lane, pointing a speed camera in my direction.

Bugger. Was I doing 44 or more in a 40mph zone? Mounted in a bright red Saab 9-3, I figured I was right in her crosshairs.

As I rolled off down Roehampton Vale I cursed the handheld camera, which I believe should always be mounted a tripod. A perilously balanced policewomen is surely not a sturdy enough structure from which to very accurately calculate my speed.

I turned into the local petrol station, continuing to curse everything. I didn’t know it, but I was about to learn about the difference between speed cameras and traffic cops.

When I came out of the shop, the traffic cops were also parked in the petrol station. They had clocked a motorcyclist and had pulled him over.

So I approached the driver of the BMW 5-series Touring traffic car. ‘I’ve just been watching you. Don’t you think that handheld speed cameras should be on a tripod?’