There are average speed camera on the M27 at the moment, signed as set to 50mph. When I keep a steady 50 through them I seem to be the slowest thing out there and yes, tailgating happens a lot. (Why?) Went in a friend's car last week, he has been commuting along that stretch of road for months. He set his cruise control to 56mph, said he has been doing it like that twice every day and hasn't had a ticket yet....