The man von Hartmann hopes to contact is the other main confected figure in Harris’s story, a young Foreign Office diplomat, Hugh Legat (George Mackay), with whom he had studied at Oxford. The German makes contact with British intelligence, who – without telling Chamberlain – order Legat to accompany the prime minister to Munich and, while there, receive the information his old friend wishes to pass over. The exchange takes place: and von Hartmann’s document returns us to the world of fact, for it is what history knows as the Hossbach Memorandum.

A summary of a meeting held on November 5 1937, the Hossbach Memorandum was written by Hitler’s military adjutant, Colonel Friedrich Hossbach, and records the moment the dictator acknowledged the poor state of the German economy and outlined a plan to boost it by obtaining territory that would provide raw materials essential to his country’s preparations for a larger-scale conflict. Hitler explicitly said that he did not want, and could not afford, a war with Britain or France, but intended to take Austria and Czechoslovakia and, effectively, asset-strip them.

By the time of the Munich Agreement, Hitler had already accomplished half of this, by absorbing Austria into the Reich at the Anschluss of March 1938; what the Hossbach Memorandum proved is that he did not intend to stop at the Sudetenland, but would soon demand the whole of Czechoslovakia.

In reality, Chamberlain was dead long before any British politician or official ever saw the memorandum: a copy of it reached the Foreign Office on May 11 1945, three days after VE Day, and was cited at the Nuremberg Trials. But in Munich, Legat engineers a brief meeting between von Hartmann and Chamberlain in which the memorandum is handed over.