To answer the general question, I am going to say lack of enforcement. If Ant hadn't crashed, he would have got away with it.
I know there are police represented on this forum who may well have different views, but my impression is that you'd have to be driving pretty badly (or in a car with an obvious defect) to run any real risk of being pulled over. The police are busy enough dealing with the general population who are unable to drive a few miles without crashing into something.
Compare and contrast with other countries who routinely set up road blocks and breathalyse everybody coming through.
I know there are police represented on this forum who may well have different views, but my impression is that you'd have to be driving pretty badly (or in a car with an obvious defect) to run any real risk of being pulled over. The police are busy enough dealing with the general population who are unable to drive a few miles without crashing into something.
Compare and contrast with other countries who routinely set up road blocks and breathalyse everybody coming through.