So - I had a lovely walk at lunch in the sun - came back to work - and found some %^*())#@$%&)*&^% customer had pressed a big wad of chewing gum into the lock on our store's front door! We've had vandalism before, but this really sucks of mindless malevolence.
Fortunately I remembered the trick of turning the can of compressed air upside down and converting it into a freeze gun.
What next? Using the flower pots as urinals?