Thanks for all the advice on this, everyone.
Took Cooper to the vets today and he's got an infection in one of his anal glands, which
I think
could account for his unusual behaviour towards Morgan
- though the locum vet (who has never met him before and didn't even speak to him or fuss him to reassure my little 'un that he needn't be scared of her
) sniggered when I suggested that the two things might be connected
She then went on to give me a big lecture about buying dogs with docked tails
and basically ranted the whole time. I'm not going back until she's gone
She had to shave round his rear so poor Cooper is sitting here with a bum like a baboon but getting lots of hugs and cuddles even though he's still stinking