Should 4x4 vehicles be allowed to use these tracks as a form of recreation? I don't know to be honest. There's no escape from the fact that they damage and tear up the ground, but then again, send enough of us walkers across here and you'd have the same result. At least they're slower and more considerate than scrambler bikes and mountain bikes who seem to adopt the "he who travels fastest has the right of way" approach.
Whatever our thoughts; technically they are allowed to drive over here. Although I should point out they are breaking at least one rule from the "Green Road Code". The maximum group size should be 4. And if you feel really strongly about this, they're also asked not to travel after wet weather. Well, it rained yesterday, it rained last night and it rained again this morning so based on that evidence, the answer to my original question is no.