It sounds like we have an open floor! I have nothing to contribute either, although, as they say in the classics, let the records show that jibbo took away the gong for this one.
I found the photo interesting. I've only been to MM the once, and I think I saw the other bridges but not the timber bridge that was the subject here. I had mentally discounted closed lines becasue the bridge looked in pretty good nick, and I thought that rails had been lifted off the MM line ages ago. The little hut in the foreground suggested (at least to me) something more recent too.
Just goes to show how assumptions can be misleading.