2 blokes knock on a door in a pit village in Yorkshire -
A woman answers "can we talk to your husband please?"
"Who are you" she replies
"We're from the CID"
"Hes down the garden in the greenhouse, what do you want with him"
"Well", they reply, "The're have been a lot thefts recently from the pit and we're investigating all houses in the vicinity"
"I can assure you my husband wouldnt do anything like that, 27 years hes worked down that pit and he is as honest as the day is long"
"We're sure he is madam but all the same we need to carry out our investigations, can we take a walk down the garden and have a word with him?"
"Of course you can, but dont walk, take the conveyor belt"