None, if the do as you likeys want it, they don't bother with the lock, they either clamp on another hitch beside the original, or they use the jockey wheel to clamp to, wheel clamps slow them down, by about 10 seconds. Sorry to sound do pessimistic, but it's the reality.
A security post or a secure storage is better.
For when storing in one place fit a ground anchor and a bloody great chain and a couple of wheel clamps. I watched a video of them nicking one and the just backed up to it slung a chain around the draw bar which had a hitch lock on, put the jockey wheel up and away they went. The whole process was less than 10 seconds and it was gone.