A music hall entertainer is stopped by the police for having a faulty brake light and, on the back seat of the car, the policeman spots a whole set of knives.
He ask the man why he has them - doesn't he know it's against the law to carry knifes?
The man explains that the knifes are used in his act - he juggles them.
The policeman insists that the man gets out to show him, so he stands at the roadside performing his act.
Just then, another car drives by and the driver turns to his wife saying, "Thank goodness I gave up the demon drink - just look how police test you these days."