p.s.
I have a 'life hammer' because I was driving an estate car quickly on a two-lane section of the A1 after midnight, when I came across large pieces of lorry tyre debris, which I tried to avoid. In doing so, I hit the kerb by the Armco and the car flipped, rolled across the road and ended upside-down in a big ditch.
Hanging by the seat belt, the first fear was fire, so I switched the ignition off, but the car was diesel and there was no sign of it. Instinctively, I then undid the seat belt and ... fell on my head. Next, I tried the door, of course, but the ditch was so narrow that it couldn't open. Nor could the passenger's, so I crawled into the back, but the doors there were jammed, too.
At this point, I was beginning to worry, but tried one of the rear-door, wind-down, don't-open-all-the-way windows and managed to get my head & shoulders out. Having got all of me out, I rolled over and stuck my head back in to see how the dog was. Sitting calmly on the inside of the roof at the back, he looked at me and said, 'What the f... was that, then?', followed immediately by 'Can we go for a walk now?'
Two days later, I was standing in a recovery yard looking at the wreck when one of the staff came up and said, 'I'll bet he didn't get out alive.' I then realised that it was probably the laminated windscreen that meant he was wrong, because, although it cracked badly and partially collapsed, it still still supported the roof. So, whether a life hammer would have broken it well enough for it to be an escape route, I don't know. And breaking the side windows would have been no use, anyway. But smashing the vertical back window of the estate might well have been a way out. Hence the hammer now.