What was the occasion for the one bark?
We had a window cleaner who the dog didnt like, it used to hide away from him, I think he must have done something to the dog
Anyway, we were at my father in laws and someone came to the door and when he opened the door the dog barked, it was the window cleaner (not ours of course)
Dont know why the dog barked, maybe the smell of him (shammy leathers or soap)
That was the one and only time it ever barked