But why?
I am insured by my insurance company for driving the car. Even if I make a mistake and cause and accident, that’s the agreement. But if my car is parked for the night , and I failed to lock the doors, and my car is ‘broken into’, many insurance agreements would exclude cover for theft. I think that’s tough, as it’s easy to do by mistake, but insurers are probably within their rights.
Why should it be any different if the owner/hirer fails to secure the car on a hill, then walks off to look at the wildlife? That’s not an easy mistake at all imho. If they depended solely upon a handbrake then it’s extreme negligence, no matter how commonplace it might be. That said, I don’t really know if insurers can use such ‘negligence’ to avoid payment, so perhaps I am being alarmist.
It’s actually one of my pet hates... people who leave a car on a hill just on handbrake, with no other precautions.
Automatic owners are even worse, as many don’t even apply the handbrake. But an auto in ‘park’ does not stop the car from rolling down a hill. Since it applies to the transmission, pre-differential, it just stops wheels on opposite sides from going round in the same direction. If one wheel is on ice, or mud, or loose gravel, ‘Park’ is useless. Highway code again offers clear advice.