Chequers, you've got my sympathy but as I think you've realised YABU to expect them to be on a lead just beacause of their breed. My poor pup was attacked by a rottweiler last week, there were 2 others circling as it attacked him. He's a 10mth NSDTRetirever and submitted completly but the rotti still kept attacking him, let him go a couple of times and then pinned him to the ground again shaking him. He was bruised but ok, we were both very shaken, him literally so. the owner said they put them on a lead when other dogs are around but I came out of nowhere - I came around a corner on the footpath, my dog was next to me, theirs were way ahead of them on the path, so far away that they couldn't see which of their dogs attacked, they asked me which it was. They offered to pay vets leads, I just asked that they keep their dog on a lead if they know its aggressive, they said they'll just put it on when other dogs are around. She also said it probably kept attacking my dog becasue he was making so much noise - he kept yelping when he was being bitten, I'm just really glad my dd (2.8) wasn't with me at the time. I've reported them to the dog warden, although there isn't much they can do other than write to them and tell them to keep their dogs under close control. Now theirs is a dog that should be on the lead.