Ah well, I'm sure there must be a good reason.

After a few years of pottering around the neighbours' fields, I'm now confined to the footpath, since this one seems to have been declared 'out of bounds'.  No more herons, ducklings, primroses, water cascades, deer prints, stick collecting, chatting to the field labourer, picking up bits of discarded rubbish, clearing logs from the little weir, washing me wellies in the stream, admiring the daffs and the bluebells, finding lizards... 
I can't remember the source, but a lovely maxim I once read was 'enjoy things without the need to own them', and I've been lucky to enjoy this for so long, I shouldn't complain that I no longer can.  Maybe it is a conservation thing?
So, a new chain, a new lock, and a new sign - I've been told, eh?