I see where they're going with this; they don't want you driving up the side of Ben Nevis or Snowdon then trying to claim when you've rolled it 97 times having the fallen off the side of a mountain. I can't see though how this could ever be enforced, the only way being that if you had an accident somewhere and then said to the attending PC, " Sorry mate, my insurance is invalid because I once drove across a field in Dorset "....