This sign is essentially in the middle of a field - it's a longish walk from the road before you reach it. Quy Fen is a marshy, protected area - no idea why there is such a long list of prohibited activities!! I remembered this after looking at @peggysirk 's random signage!!
How very bizarre - are nudists likely to trek for ages from the road to a rather marshy bit of land to do their naked thing? Thought they liked beaches and playing tennis and stuff. Or maybe that naked rambler chap has been rambling this way ...