“I’ve nev­er seen so many weak blad­ders,” said my part­ner, as yet anoth­er sil­hou­ette shuf­fled out, block­ing the screen dur­ing North­ern Soul, the film by Elaine Con­stan­tine. “It’s because every­one here is ‘of a cer­tain age’ ”, I replied. Indeed, about 90 per cent of the audi­ence did look as if they could remem­ber North­ern Soul,…