Uncut Gems, writer-directors Josh & Benny Safdie’s fifth feature together, starts full throttle and only occasionally lets up. It is fixed to the world and worldview of Howard Ratner (Adam Sandler), a jeweller for the stars in New York’s diamond district: a chancer and grifter, thriving in an ecosystem of insatiable avarice. As it becomes rapidly clear, he is a man that gets both a hit and an identity from triumphing over the constant barrage of knife-edge negotiations and impossible odds. Or, failing that, just surviving them. Ratner juggles his family life, with kids he is provisionally interested in and…