I've been caught twice.
First time was near my house where the straight road goes from 40 to 30mph (school further up the road where at least one person has been killed and speed limits are broken a lot, but they won't park up there, only on a road that has had zero accidents ever. They can claim that the presence of the van has prevented so-and-so I bet)
Tues or Thurs are the days the camera vans pop out in my town, and I could see a good half mile ahead whilst in the 40mph zone where the van was.
Slowed and my digital speedometer said 30mph all the way past the van.
2 days later, I got a luminous green letter saying I was doing 35mph.
Zero way of proving otherwise unless I was filming the road and my speedometer etc. at the time.
Had to pay £90+ for a speed awareness course.
Second time was on the M1 just past Meadowhall.
Driving along at 59mph as no real rush at 1:30-2:30am on the way to Manchester.
Two other cars in the lanes to my right went zooming past at some speed.
The overhead gantry camera double flashed for me as I approached, but not for them.
Motorway awareness course in Hull for that one.
Do lorries ever get picked up for speeding? Every time I've ever been in "average 50mph speed limit" zones, with cameras, every lorry overtakes me and pulls away whilst I'm using cruise at 50mph.