Harold Ratner, the luckless protagonist of the Safdie Brothers’ new film, inspires devotion. Such devotion, in fact, that his girlfriend has his name tattooed to her behind. “Howie” it says, in demonstration of unwavering devotion. Only scenes earlier she had been caught in a club-toilet with the Grammy-winning popstar, the Weeknd, much to Harold’s impotent outrage as he is booted from the VIP shindig. No doubt, devotees of the young New York filmmakers will be tempted to have similar etchings on their posteriors. “Safdie” they might say, such is the brilliance of the brothers’ new film: an exhilarating, if heart murmuring, cavalcade through New York’s Diamond District and beyond.