The Irishman is Martin Scorsese’s three-and-a-half-hour epic — a mobster-a-thon, you could say — starring Robert De Niro, Al Pacino, Joe Pesci and a light sprinkling of Harvey Keitel (he’s only in a couple of scenes). It’s based on the true, late-life confession of Mafia hitman Frank ‘The Irishman’ Sheeran and, while gangster flicks can often leave me cold and sometimes baffled — he was dispatched to sleep with the fishes for why? — this is magnificently engrossing.