A man dies and goes to heaven. Behind St Peter, he sees a whole load of clocks in all shapes and sizes.
"What are those?" he asks.
"Oh," says St Peter, "they're lie clocks. Every time a person lies, the hands move forward. That one there belongs to Nelson Mandela. Its hands have never moved."
"Whose is that one?" the man asks.
"That's Abraham Lincoln's. Its hands have moved twice."
"Where's Boris Johnson's?"
"We're using it as a ceiling fan."