Do not even bother having a go at these types. I was kindly threatened with a kicking by a charming group of 3 gorilla's on bikes, in front of my wife.
This was near Brockely Coombe, by Bristol Airport, which has seen massive destruction at the hands of MX'ers and 4×4 brigade. At least it's dry at the moment and so damage is limited but the state of the Brockely Coombe to Wrington bridleway is staggering considering i used to use it to commute home on (when it was mostly grass double track with the odd puddle).
Also, can someone explain how the new big gates stop 4×4's when they always seem to be open?!!