This reminds me of an incident a few years ago- also in High Wycombe, which i was told about by the policeman himself:
He was driving down a winding road and saw a car parked precariously after a blind bend, with its hazard lights on. He stopped and got out to lecture the driver, saying he obviously knew he was causing a hazard, as he'd put his lights on, what if a car came round the bend and didn't see it in time? Etc, etc. As he was saying that, another car drove round the bend, straight into the back of the police car. He said he'd never been so embarrassed!