This law mandates that any dog in a public place must wear a collar with the full name and address of the owner, including post code, engraved or written on it, or engraved on a tag attached to the collar. Your telephone number is optional (but advisable).
There are some exceptions to this order – mainly relating to working dogs, but the owner must have proof of lawful authority on him.
This order gives the local authority powers to treat such a dog as a stray. (Note: this does not empower police).