Free Fighting to Lose by John Bryden

services, MI5 and MI6, had become somewhat musty over the economically parched years of the 1920s and ’30s. There were no fresh brooms to sweep their porches of entrenched ideas firmly rooted in past experiences.
    The double agent, for instance, was still a novel concept to Britain’s handful of counter-espionage officers in the late 1930s. During the First World War, it was government policy that spies captured in the United Kingdom were invariably to be either imprisoned or executed; there was little incentive for Vernon Kell’s Security Service — first MO5g and then MI5 — to experiment with having them continue to report back to their spymasters as if still free, and so be used to feed the enemy disinformation. Twenty years later, little had changed.
    In 1938, however, following talks with the French Deuxième Bureau, MI5 decided to give it a try. A Major Sinclair was assigned the task, but progress was modest, given that before the Second World War the resources for finding spies in the first place were meagre. Britain in peacetime largely respected the customary rules for freedom of movement and individual privacy.23
    The predecessor of the Secret Intelligence Service, on the other hand — Mansfield Cumming’s MI1(c) and then afterward MI6 — had used double agents extensively during the First World War, especially against the German secret service operating in France and neutral Holland.24 MI6 continued to use them in the interwar years against a new adversary, the intelligence services of Soviet Russia operating in the countries of Western Europe. MI6 officers were posted as passport control officers (PCOs) in the embassies abroad, where they screened for possible spies using the simple but ingenious principle that it would be necessary for all foreigners heading for British territory to check in first with British passport control.
    Not much is known of the codes and ciphers used by the PCOs and their sub-agents during the 1930s, but apparently they were not of a very high order. For the most part, intelligence collected from spies in foreign lands could be sent back to England by diplomatic bag or mailed, and it was assumed that other countries did the same. As for MI5, it relegated “ciphers” to its female support staff, so it can be safely assumed that when the war began in 1939, MI5 officers were largely ignorant on the subject.25
    MI6 had had an advantage. Unlike the United States, which dismantled its wartime code- and cipher-breaking agency in the late 1920s, Britain’s Foreign Office saw to it that the Admiralty’s similar and spectacularly successful “Room 40,” and the code-breaking unit of the War Office, MI1(b), were retained with their original staffs largely intact. Reorganized as the Government Code & Cipher School — a cover implying only oversight of government ciphers — its real mission was peacetime espionage, the primary target being the intercepted enciphered telegrams of foreign diplomats. This properly put its twenty-five cryptographers under MI6 and its chief (after 1923), Admiral Hugh Sinclair.26
    British intelligence — the term encompassing all government organizations with an active or potential role in foreign intelligence gathering — extended its reach to all international communications. By 1939, through government carrot-and-stick policies toward private corporations, all but a handful of the world’s undersea telegraph cables passed at some point through British or Commonwealth territory. It was the same with the international mails. Most letters posted from one continent to another had to go through a British choke point. This enabled MI6 to have almost anyone’s overseas letter or telegram intercepted and looked at. It was a remarkable achievement.27
    MI5, of course, could have letters and cables intercepted at home, but, with the onset of war, its requirements took firm second place to those of MI6 and the intelligence departments of the armed forces. MC1