Wow! Brilliant to see so many replies and interesting thoughts!
I'd never considered that it could be a mock-up but that is certainly a possibility that I find intriguing.
I have to say I'm not sure about the 'eagle'. To me, it looks like a dome that extends up into ceiling with something hangin down in the middle (the white part). The perspective gives it the oval shape and the cut out gives the shape of wings! I've seen a smililar thing before.
Just to throw some more thoughts in...
Having spoken to the photo owner, it seems doubtful that it's in Sussex (which was my initial thought) and more likely to have been Scotland or London!
We notcied another set of metal work (similar to a bed head) behind the bed and behind the railing which we wondered what they actually were (image below). We were also slightly spooked by the shape of the figure to the right of the image...A shadow I hope


Thankyou very much for the re-touch Prue, I had actually re-touched it quite a bit from the orginal (to the best of my ability) but you've certainly revealed much more to me!
There are in fact two very nearly identical glass negatives that I found, they had some sort of brown tape around them and came in a cardboard mini folder from a photographer now I come to think of it. I'll try and find out what was on the folder.
I've linked to the original scan
here if you want to see it. I inverted the colours and adjusted some levels to get to what I first posted. Thought you might like to see the original if you want!
Thanks for all the replies so far!!