I was wondering: British law allows one to use a reasonable level of force in defence of one's property. But isn't this much harder to benchmark than in cases of defence of your person? What is a reasonable amount of force to use if you find someone trying to saw the chain off your bicyle or climb in through your window? It's tempting to say "kick the dung out of them", but what is the goal for which the force should be proportional? To affect a citizen's arrest? To discourage them from the crime in progress?