I put the hood up or a cockpit cover or tonneau. I tend to lock the doors but only because I have heard not doing so invalidates insurance if anything does get damaged or stolen. But never had any problems. Most joy-riders would not be seen dead in an "old git`s car" even if they could mobilise the brain cell to work out how to release the handbrake! (do leave it in gear - not called a fly-off handbrake for nothing!) also no commercial theives would be able to sell it on.
Engage common sense when leaving the car.
