Be careful out there!

Serves them right for living in a place called "Bogend Toll" - though will watch for that one as it's on the way to a mate in Scotland...

Apparently the 20mph SPECS along embankment were first used to give warnings to people - they got letters through telling them how fast they'd been clocked and that in future they'd get busted if they did that sort of speed. That seems to be the way SPECS is started elsewhere - I remember one trial displayed the number plate of the speeding driver with their speed and a big "slow down" on some roads, to embarrass them into slowing down. Not heard of anyone being given a penalty from a SPECS camera yet, though there must be plenty, especially around the 20 limits.

Another fault with SPECS (though maybe bikers being SPECS-proof is not excatly a fault) is that if there is slow traffic for part of the distance measured, there's no mechanism to tell whether someone has gone well over the limit for part of the distance.
Example - slow moving traffic at 5mph, Mr BMW gets the hump, it clears, he rockets up to the ton in a 30 limit, then gets stopped by more traffic at the next junction, yet his average speed was under 30, so he's "safe".