When Benjamin Clementine won the Mercury prize a fortnight ago, some critics described him as obscure. Well, up to a point. Although the singer and pianist’s debut album only entered the top 40 post-Mercury, his first major press interview and a live review appeared in this paper almost exactly two years ago. So while there were new admirers at this sold-out show, Clementine’s no overnight success. A lengthy spell in Paris busking on the Metro is part of his mythology, along with abject loneliness when growing up in Edmonton.