When the United Kingdom handed Hong Kong back to China in 1997, China said it was an opportunity to put the past behind them. Britain’s newly elected prime minister Tony Blair would later admit that at that time he had “only a fairly dim and sketchy understanding” of what that past was. There would be many in Ireland who would feel a pang of familiarity at this passage as it appears in Sathnam Sanghera’s absorbing new book ‘Empireland’. Britain: The Brexit Years led to weekly outrage as Ireland responded to some ahistorical assertion from a Brexiteer or just absorbed a…