Thirty-one men held the position of Foreign Secretary during the twentieth century, usually – though not invariably – being one of the two or three most significant figures in Cabinet. This book provides profiles for each of them, both as standalone essays and as part of the wider story of how the holders of the office have developed from being landed grandees to run-of-the-mill politicians; from largely independent practitioners of foreign policy to playing a supporting role behind their Prime Ministers; and how they oversaw Britain’s decline from the preeminent global superpower to a second-tier state with sharply circumscribed freedom of action. The book will examine the journey from Henry Charles Keith Petty-Fitzmaurice, 5th Marquess of Lansdowne, scion of an ancient family, through to Robin Cook, grandson of a miner.