Alongside sliding towards a hard object, backwards, and realising that you aren’t going to be able to make it around the next corner, the double flash of a GATSO going off in your rear-view mirror is one of the most dreadful experiences you can have on four wheels.

It happened to me earlier this week, at five in the morning, on a section of the M25 on which I must have traveled at least a thousand times in the last 10 years, often at the exact same speed that I was doing this week.

The trouble with GATSOs, somewhat annoyingly, is that you can never tell which ones are switched on and which ones are switched off. Most of them are switched off, but this particular one – mounted on an overhead gantry between junction eight at Reigate and junction nine at Leatherhead going anti-clockwise – has been sat there for years, doing not a lot.