A Scouser is driving

A Scouser is driving through Liverpool with his dog in the passenger seat.
A police panda car follows him for about half a mile and then puts its siren and stop sign on, indicating to him to pull over.
As the copper approaches the car, he sees the Scouser is slapping the dog's head.
He tells the driver to wind down his window and asks, "Why are you hitting the dog?"
The Scouser replies, "The bloody thing just ate my tax disc."