When I was young and playing out in the street on my own, my mum said to me

“If anybody you don’t know tries to get you to go somewhere with them, scream “BLUE MURDER!.”

Now, I was convinced that I had to shout “blue murder, blue murder” and for many years I wondered what blue murder was and why it was never mentioned on any crime programmes. But like the sixpences, I found out one day.