This is a book about the political influence of an idea and a movement dedicated to the creation and building of a federal Europe in the late 1930s, culminating in the historic British offer, endorsed by the British prime minister, Winston Churchill, of a Franco-British union in June 1940 that would form the basis of a larger European Union in the future.

Andrea Bosco has written a splendid account of the dramatic events of 1938–40 that occurred in Anglo-French relations, during which British and French governmental elites sought to work out a strategy to keep France in the Second World War at all costs in the face of the German Blitzkrieg that threatened to overrun the country. At its heart is the notion of “crisis” and the opportunities created for both federalists and nonfederalists alike to make momentous decisions that would in all likelihood be considered chimerical in normal conditions of peace. This understanding of crisis and the constitutional and political choices made available of course relies in particular on bold and imaginative political leadership and on timing. And it is a federalist political strategy most closely associated with Jean Monnet, the French international civil servant—often referred to as a functionalist-federalist—who later in 1950 wrote the Schuman Declaration and became both the architect and builder of the first post-war supranational organization, the European Coal and Steel Community, established in the Paris Treaty of 1951. Capitalizing on crisis was a similarly integral part of the federalist strategy of Altiero Spinelli, the leading political figure in the federal movement in Italy and the then European Community, who fought for a “constitutional and political Europe” while himself working during the 1970s and 1980s in the European Commission and European Parliament.

Bosco's approach to identifying the political actors and organizations involved in this remarkable episode is to provide a sharp focus upon the following institutional and political contexts: the Federal Union movement; the New Commonwealth Society; the Pan-Europa movement; the role of the Foreign Office; the federalist debate on war aims in the British, French, and American press; the influence of Chatham House; and the important insights into the discussions on federalism in the War Cabinet. The key dramatis personae at the heart of this movement included Jean Monnet, Lionel Curtis, Lord Lothian, Lionel Robbins, Arnold Toynbee, Alfred Zimmern, Leo Amery, Sir Arthur Salter, Sir Robert Vansittart, Winston Churchill, and his private secretary, Desmond Morton. For the sake of brevity, I have singled out only a small coterie of public officials, academics, and federalist enthusiasts, but Bosco has identified an enormous array of political actors across the whole spectrum of the British Establishment whose individual activities can be construed as a complex network of interactions that together formed the basis of the political influence mentioned above.

Some of the material included in the book, especially on the Federal Union movement, is already well documented in the mainstream literature (to which Bosco has himself contributed), but in providing such a detailed account based upon archival sources previously unpublished, he has effectively set it in a much more fertile context than previous accounts, notably by John Pinder and Richard Maine in Federal Union: The Pioneers (1990) and by Walter Lipgens in his magisterial A History of European Integration: The Formation of the European Unity Movement, 1945–1947 (1982). Bosco's work presents us with yet another important dimension of the larger British federal tradition, dating back to the Imperial Federation movement in the late nineteenth century and the Round Table movement in the early twentieth century. These movements corresponded to the shift in British imperial policy—from empire to Commonwealth—in the wake of the growing independence of the white self-governing colonies and the pressures to look increasingly during the interwar years to the United States of America and a more Atlanticist perspective of the future.

It might have been useful to have emphasized more strongly the evidence of Churchill's previous dalliances with the federal idea—commonly dubbed federal devolution—for the United Kingdom as a whole just before the “Great War” of 1914 and as a direct response to the perceived “crisis” of Ulster in the Liberal government's Irish Home Rule policy from 1910 to 1916. His famous Dundee speech of 1912 is a case in point. This would have given more credence to Churchill's attitude and behavior in terms of his insistence that “we must not let ourselves be accused of a lack of imagination” regarding the notion of a perpetual Anglo-French union in June 1940 (304). Although he was the British prime minister in June 1940, having rejoined the Conservative Party, he was never averse to “thinking outside of the box,” and there was evidently still something of the young radical Liberal Churchill in him who had always been open to imaginative proposals and often willing to consider turning them into practical policies. Bosco provides some support for this view when he notes that although Churchill remained skeptical about this proposal he was persuaded to endorse it by the unexpected enthusiasm of his War Cabinet colleagues (300–3).

Bosco's detailed analysis of the relationship between the different institutions and actors at the center of this epic struggle to build the foundations of the first European Union from 1938 to 1940 and his portrayal of the rollercoaster events and circumstances that characterized Anglo-French relations on the eve of the invasion of France by Germany conveys a strong sense of tension and excitement that is now quite rare in accounts of modern political history. Bosco brings the subject alive, and from a purely British perspective he is right: 14–16 June 1940 and 22 June 2016—77 years apart—were both turning points in British constitutional and political history. The former “indissoluble union” proposed during a real crisis was stillborn, while the latter “ever closer union” was narrowly rejected in a British referendum—arguably based upon the misperceptions of a crisis—that probably should never have taken place.