I didn't hear it, but I did hear the earlier (a year or two ago?) interview with Eliza on Womans Hour, in which she also sang unaccompanied.

Nothing strange about about that to most of us, but we're all folkies and used to it. Your average citizen/ Radio 4 listener does find unaccompanied singing strange because it's very rarely heard in the mass media. I remember how unusual it seemed to me, when as a student I was dragged to a folk club for the first time by my friends. I actually felt embarrassed, as if they were standing up stark naked in front of the audience!

Anahata