a singer who's probably only listened to by a very small minority of middle-aged, middle-class British people

You think "the Godfather of soul" doesn't have a following amongst Brits of all ages and skin colorations even today?

Do you think there is any Brit of just about any age who hasn't heard "Papa's Got a Brand New Bag"?

Do you think they stopped broadcasting popular music from the 50's and 60's in Britain 35 years ago?

I agree your "popular theory" may be right, but a "popular theory" is just a theory -- just like mine. :)

Who's your daddy, Capfka?