My lock was rubbish, so I added this (there are plates on the other side - bolts go through):

Camper is left completely unlocked at home so if anyone wants to nose around they can rather than damaging it. So this is not to secure the camper when left unattended in an insecure location, but more to stop the sort of fast break-in you might get when a vehicle is left on a street during the day.
It does have a much stronger rubber-coated padlock on there - the one in the picture is just to test it out.
So again, not aimed at stopping someone with a pry-bar willing to make a lot of noise (we avoid parking places where they could get away with a noisy and messy break-in). It also is designed to look like the homer it is - that sort of "my locks broken so I fixed this on quickly" look, combined with "I am too poor to afford proper locks, so if you do break in you'll just find a camper full of more worthless broken stuff" (there is a good degree of truth in both statements actually).
Steve.