I spent a wakeful night worrying about Lily - looking up the links and suggestions that Lucy had left me in the comments. I came down this morning and prepared a bowl of live yogurt and olive oil as I was convinced she was crop bound.
Unfortunately, when I went down to her early this morning, she had died in the night. She was in the nest box and Flossie was worrying at the door.
I'm feeling guilty that I didn't spot anything earlier but I'm hoping that she didn't suffer. Flossie seems to be quite happy going about her business at the moment, although she hasn't laid yet today. I guess I should think about replacing Lily as I don't think hens are solitary creatures.