Irish Londoner Harry Hambridge is not the kind of hero you would ever imagine: overly fond of lager, over-weight and underachieving; yet when, back in the home of his feisty Aunt, he comes across an extraordinary testimony from his Grandfather, claiming that it was he who hoisted the Irish flag on top of the GPO during the 1916 rising and that the self same flag was hung upside-down in an army barracks in Hampshire, Harry knows his long awaited call in life has arrived.
But getting the flag back isn’t quite as easy as he’d imagined. After trying, and failing miserably, to reclaim the flag through legal means, Harry and his motley gang drunkenly plan a heist on the barracks. Sure it can’t be that hard, right?