It's a bit clearer in Scotland, travel for excercise is allowed if it starts and finishes in the same place and that place is no more than 5 miles from your county boundary. It has led to a bit of map searching for some, and to complaints from people living in small counties, and envy of those with highland addresses, but at least you know where you are. For me, 5 miles would land me in the sea, and there are large chunks of the county I can't get to without breaking the rules about avoiding public transport (ferries), but actually it gives quite a bit of room for manoeuvre, and at least I know what the lines are, even though I tend to keep more local than I have to.