Roger Hayter wrote:
Unfortunately the wall is loose slate stones and not solid so any free
side fitting will have be cantilevered out from the hinge side post or
from something buried int he path inside the wall. Not impossible, so
thanks for the suggestion. But if I am doing this a bolt would work
too.

A bolt that goes into a hole in the ground, like the bolts you get on a pair
of gates/doors where one locks and the other is only openable once the
locking one is open and gives access to the bolt? It would depend how high
the wall is as to whether there's enough space to stow it in the 'up'
position and swing it over the wall.

Theo