Oh Reg - be careful. That would be just a perfect space to run a fence line (hardware mesh of course) from the wooden fence, right to the house. A simple door for you to get in and out, a low roof to keep out predators (I know you don't see them, but I would bet you have racoons and hawks), and the hens could have that whole back part of the yard. I can see you sitting outside in the yard for an hour or so of hen time every day!! Come on - let's give them the whole back yard....
If i get Racoons in England I will make the evening news. LOL
Sparrowhawks, Foxes, Cats & me are them main problems the hens will have.