Thank you, Richie, for your reply. This is more or less what I suspected. But it does seem such a complicated and murky question. I have seldom heard a melody that didn't remind me of an earlier piece and I occasionally wonder just how close that resemblance would be before someone goes looking for a lawyer.

I suppose it helps to keep lawyers in work. We all know how much they need the money.

And I've just half-remembered seeing Martin Carthy in that documentary on BBC4. If I remember correctly he was saying nice and admiring things aboout Paul Simon.