Not REAL coppers but when I was in the RAF we used to talk to the dog when the RAFP (police) were trying to act the big one.
We used to get allot of junior RAFP would try to pull rank and feel powerful, stupid things like trying to get you for walking on the road instead of the pavement coming back from the bar etc.
The RAFP get an acting rank status the next rank above their own, this is to give them a level of authority. The dog's however get the actual rank on completion of their training.
Thus the dog is actually higher rank than the handler in most cases.
Hence they stop you on an evening you turn and address the dog. Yes, you're a good boy corporal.
What's that corporal? You want a biscuit? A walk?
Good times