Its going to be the signal interference problem that I've tried to point out on here a hundred times, but nobody listens.
There is definitely several different types of things that mess with ACC and the city breaking/parking sensors.
I suspect that the Tyne Tunnel problem is either a static piece of electronic equipment at the tunnel or some other car's electronics screwing with it.
Who said that?
The static piece of electronic equipment at the Tyne tunnel is likely to be the RFID tag reader that reads my unique tag associated with my Tyne tunnel toll account (so I don't have to handle cash at the tunnel). It has happened once elsewhere on a long sweeping bend of the A1, but 6 times out of 7, it has happened at the North side of the tunnel when approaching the toll gates, but well before the point that the tag reader would read my tag, deduct my toll from my account and open the barrier for me, so it may not be that.
The common denominator at all incidences has been a long stretch of road, on a constant curve - maybe every once in a while it needs to lock onto something for readings to remain plausible, and a bend lasting 1/2 a mile in the same direction puzzles it?