A very long time ago, soon after passing my test, I was driving home through Weymouth in my Mother's car, about 2am, and became aware of a car tight behind without lights. So I gradually increased speed, until at about 50mph, in the 30 limit, the blue lights came on. Turned out, the car was a police car. Bored policeman, saw the only car he'd seen for ages, so followed. Forgot to turn his lights on under the streetlights. Despite him thinking he might still do me for speeding, I did get an apology.