I'm pretty sure our house got targeted yesterday by someone who wanted to see if it was vacant, with the intention of breaking in if they knew we were away.
When we got home last night, we found a little bit of foliage from one of our plant pots poked in the lock of our gate. It seems like the system is that if they return the next day and find that whatever is in the lock hasn't been removed, there's a decent chance that the property isn't currently occupied and so is a better prospect for burglary.
Has anyone else experienced this? A bit of searching online reveals a similar technique using sellotape over a lock. When we phoned 101, the officer had no idea what we were talking about, and suggested it was "a joke", but couldn't explain what the punchline might be.