'A song against post-punk tribalism, inspired by a 1979 concert at Camden's Electric ballroom when they opened for Orchestral manoeuvres in the Dark and Talking Heads, it shows how even in their earliest days, Edge and Adam Clayton could integrate a riff so guitar and bass locked together to double its impact. The song also has Virgin Prunes links, its title coming from a note pinned to the door of Bono's home by Gavin Friday after the former had forgotten a meeting.'
Bill Graham in The Complete Guide To The Music of U2