A delivery man was driving along in his smart grey van, but every mile or so he stopped, got out and banged its sides with a mallet.
The policeman followed him for a while, then stopped the van by the roadside and asked the driver what he thought he was playing at.
“Well, it’s like this, officer. I’ve got two tons of canaries on board but it is only a one-ton van.
So I’ve got to keep half the little buggers flying around or they will all perch and wreck its suspension.”