Report Matt........just how did you sound??!!
P
From Pistonheads and written by and engineer on the tunnel:
There are average speed check cameras at each end of the tunnel, set for 70mph traffic (what speed they will catch you at we are not told, I'd imagine 79-80)
The average speed check cameras are variable, so are able to catch you speeding when it's 70mph OR 40mph in contraflow.