If there is a top civil service adviser to the British government on imperial affairs in the early twentieth century whose influence was such that his biography is long overdue, it is Lionel Curtis. And in the context of recent Irish history, if there is a person whose role in shaping the British conception of the 1921 Anglo-Irish settlement has yet to be fully appreciated or analysed, it is again Lionel Curtis. Lord Longford’s references to Curtis in Peace by ordeal give some indication of the influence his ideas had on British cabinet ministers before and during the treaty negotiations in the summer and autumn of 1921. But a much fuller and more systematic survey of Curtis’s association with Ireland over a broader period is needed to measure this extraordinary man’s imprint on Anglo-Irish relations.