If I remember my "Home Office" guidlines the speeds for prosecution are _

Speed limit, plus 10% plus 2 mph

Hence 30 limit = 30 + 3 + 2 = 35 miles an hour

70 = 70 + 7 + 2 = 79 mph

Mind you I have known a case of a butty of mine being done for doing 77 mph on the M20 - just out side Maidstone, Kent. And no - there were no roadworks.

The summons spoecifically menntioned that speed.

What was even more interesting was that about 20 mins later I went through the same speed trap in an identicall company issue ASTRA at about 80 mph, and was waved through.

But then John, my butty, was not exactly white.

Gareth