At LHR yesterday the lady performing a random hand search of my bag before check-in recommended that people always have a lock on their checked bags.

I guess I must have looked like a clean person as she did not bother with the rubber gloves (that were sittung on the table) when going through the bag As an aside I don't think she did a good job of checking the (very large) bag, she looked through the books at the top of the bags and then just asked "is the rest just clothes?", before putting an inspected sticker on it and walking it (and me) past the x-ray machine and up to the check-in desk.