Hi Poppops and Tenaille
Thank you for your ideas. Thinking about it, we do live in a rural area so not much traffic but they have just started harvesting all around us so it could be that he can hear tractors etc and maybe even Mice trying to find a new home. We always have a few trying to get in this time of year, its inevitable living on a farm.
We also have Bentley's sister BumbleBee that lives with us and of course once he barks she does too. I have started to tell them shhhhh and Bumble looks at me and stops straight away but Bentley keeps on eventually developing his bark into a long howl like a hound, which is terribly funny. At this point I go to him as I think this howl is fear, I scoop him up and sit with him still shhhing and gentle holding his muzzle and he goes from a howl to a moan and then stops. I will try treating him when I call him away too. I sometimes wrap him in a blanket too. He loves this because he was hand reared as he has a cleft palate. He is a big baby really but I don't mind, its part of his personality.
I will keep you posted, thanks again.
Gilly