A man is driving from Aberdeen to London, and stops in dundee to fuel up, as he is filling the tank, his passenger takes out a cigarette and starts smoking it.
Unbeknownst to the driver, when the fuel started pumping, some splashed onto the sleeve of the jacket he was wearing.
Anyways, he goes and pays for his fuel and they set off again, 5 minutes later a spark from his friends cigarette gets caught in the airflow in the car and lands on his arm which had been doused with petrol 5 minutes previously, and his arm catches fire.
The driver, in a fit of panic hangs this arm out of the window and starts waving it furiously in the breeze, trying to put it out, when he hears sirens behind him, from a police car.
The policeman approaches the car, as the man has almost fully extinguished his arm and says;
"I'm sorry sir, i'm going to have to arrest you for posession of a Firearm"