If there is no registered owner (which I thought was impossible these days) then the police should not be able to take action if you smash the window, release the handbrake, and move the car to a more convenient parking place (like the middle of the road, where the police would find a way to take action)!

Why does life need to be so easy for careless idiots and so difficult for those of us who occasionally try to obey (and rely on) the law