Well Lily's in today, and Bramble's close by. Getting Lily in was like living in the pages of the Beano! I put some of her favourite food inside the back door, then left the door ajar with some string tied to the handle, and trailed the string around the corner and waited. As soon as I heard the bowl move I pulled the string and caught her!
It's only thin string though, so if I want to try this trick with Bramble I'm going to have to find something stronger. She'll probably hurl herself at the door if she sees it closing!