I noticed them a few months back. So I decided to take a closer look and found that it was not actually the camera sitting on top of the gantry that flashed but a camera fitted to the left side of the structure.
I was unaware they flash without tickets being issued.
This is the kind of change that should be all over the papers before going live.
A "friend" has been flashed on the M1 doing over 100 in the middle of the night and no ticket arrived.
As I said before if there is a variable speed limit on do not speed, if not you are fine.