'It's good to have a bastard,' says my French friend Mathilde. 'A love child usually has a much better temperament.'
I am so shocked I almost drop the phone, as Mathilde is normally so polite. And then I realise what she means. Biff is indeed un petit batard - the (not impolite) French way of describing a dog of mixed race.
But the question of Biff's parentage has occupied me for some time now. At first, I thought he might be a mix of cocker and poodle - particularly since he doesn't shed his hair. Then I began to think he might be part Tibetan terrier. Many people in the local park in London seem to think so.
Today, however, I think I have found the answer. Looking at the pictures of Bo, the Obama girls' new dog, something looked very familiar about its shaggy features and eager-to-please expression. No doubt about it: there was a very strong resemblance - in facial features at least - to Biff.
I read on and discovered Portuguese water dogs don't shed their hair. And since Biff was thrown out of the back of a van somewhere near Bergerac - ie not that far from Portugal - it would all add up. Biff's mummy or daddy might well have been a Portuguese Water Dog.