Churchill’s dire warning still echoes down the years; indeed, it resonates in this century too. The denial of justice and the rule of law to individuals in Russia and its client states offends against the principles of Magna Carta. And Vladimir Putin’s denial of national independence to Ukraine threatens the principle established at Waterloo. The European Union and Nato have failed to assert these principles with sufficient energy to deter Putin.

The British have voted to hold an in-out referendum on EU membership, and the result will ultimately turn not only on economic arguments about the costs and benefits of membership, but on the underlying question of sovereignty. The principles of Magna Carta and Waterloo are not obviously compatible with the EU’s principle of “ever-closer union”, the consolidation of political and legal power in a united Europe. The referendum is intended to resolve, once and for all, the tension between British traditions of parliamentary democracy and the constantly growing and largely unaccountable authority of the European institutions. But a referendum cannot prevent the emergence of a eurozone with its own rules and momentum within the larger structures of the Union. As the collapse of the Greek economy over the past two years suggests, those structures are being tested and may not prove strong enough to withstand the forces that have been unleashed. The British are mere spectators in the Greek drama, but we are uncomfortably aware that its consequences will affect us too.

The continuity of British foreign policy means that periods of isolation, splendid or not, are a necessary price to pay for upholding our principles. The EU has its own continuities, but at present it is unclear whether its members are prepared to adapt its rules sufficiently to enable the Union to survive into a new era. The British choice is an unenviable one, but in the past they have always chosen to preserve their own principles and traditions rather than surrender national independence. Just as Churchill felt that appeasement was a betrayal of everything that Britain had stood for, so the British today will not vote for the EU at any price. Just as the British must not expect our partners to give up their vital interests to keep us in, so Europe must not expect Britain to sacrifice principles that we regard as permanent aspects of our national identity.