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Mine attacks no-one, ttt, but he does jump up barking at visitors as they are about to leave. On the odd occasion, he has been known to tear an item of clothing. The bill, of course, comes out of my pocket:-(
When we're up on the grassy area, and he's off the lead, he is perfectly content with strangers stroking him, especially kids.
When i said there may be more to it, i wondered if the dog has done this sort of thing before.
The old guy is 85 and it's highly unlikely he'd get another dog.