So the (former) Portuguese neighbour has been visiting on a nightly basis for aperitifs. This week I even cooked him dinner.
Biff however, is not very impressed. In fact he goes berserk - practically bouncing off the walls - whenever Luis arrives and starts a futile attempt at dominance by barking furiously and desperately trying to get himself to a more elevated level (jumping on the back of the sofa or even standing on top of the kitchen table.) My (former) Portuguese neighbour just laughs at him - or gently blows air into his nostrils - which makes Biff even madder.
The problem, I think, is that my little black dog likes to be the centre of attention and cannot bear to be ignored. He recently spent an entire night barking and making whimpering noises outside the bedroom door. But he got his revenge in the morning when he made off with my (former) Portuguese neighbour's t-shirt, shaking it furiously as if trying to kill it and forcing Luis to engage in a protracted tug-o-war to get it back.