'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. I really like the idea as that would mean that the two men in my life hail from the same place.

Biff and Bo? They'd go together quite nicely. Except in his pictures he looks a little smaller than the Obama dog.