Do all speed cameras flash?

[Christmas themed thank]

I was driving on the M1 and M25 the other day and I was in a few variable speed limit zones (that were active). I think I may have gone over the speed limit in one zone (which was 30MPH) - would I have been flashed if I had? Do all speed cameras flash?

 

[Christmas themed thank]

I should say, it was dark at the time I drove through it.

The ones in the variable speed zones generally do.

Are you sure it was 30mph though? I've never seen a variable limit less than 40 on the motorway I assumed that was the minimum they'd do.

The gantry before was 40MPH and then this one went down to 30MPH - I was shocked.