You could have the biggest dog you want But in a court of law if a possible perpetrator jumps your fence gets bitten and then turns around saying his kids lost a ball over your fence and he was trying to retrieve it.Without the back up of cctv it`s your word against his ! He can aslo argue that you had no signage of a vicious dog nor the dog had a yellow collar should of been muzzled under the hazardous dog clause?
If your dog is going to attack an intruder you better make sure you have public liability insurance !

I had an incident last summer , when i heard my car door handle in the driveway.
when i yelled out the window the 6' tall car brealer told me to F off and mind my own business,as he was only looking for coins to buy ciggies!
buggered if i was going outside in the dark.
He wandered off down the street checking every car on the street and up the driveways. when the police arrived with their dog ,the dog was straight on the scent, and would go to each car in turn and stop and signal to the police handler..
the guy wasnt going to get away as the dog was traveling alot faster,and enjoying itself