Hall led Amos Peaslee to the stacks of decrypts, gave him the run of the house, including servants, for as long as he wanted, and went off to Scotland on a shooting holiday. Three days later, Peaslee had found and copied 264 cables and radiograms pertinent to German First World War covert operations in America.
The decrypts ignited a blaze of publicity when the case was heard in The Hague in 1927. The German government may have had its suspicions, but it had no idea of the extent to which the British had been reading its secret communications, and probably still were. The immediate and lasting consequence was the Government Code & Cipher School was locked out of all German Foreign Office and German army traffic, the Foreign Office switching to unbreakable one-time pads (single-use sheets of random letters whose numerical equivalents are added to those of the letters in a message to encipher it) and the army to high-security plug board ciphering machines (akin to early telephone switchboards, they allow for the creation of thousands of unique electronic circuits).8 It stood to reason that the Abwehr, the German army’s secret intelligence service, would have taken similar measures.
To make the breach in secrecy even worse — and it could hardly have been — the types of German ciphers compromised were subsequently described by the American cryptologist Herbert Yardley in the popular book The American Black Chamber (1931) and in detail by Helen Fouché Gaines in her Elementary Cryptanalysis (1939). The most vulnerable had been transposition ciphers, which at their weakest were solvable by anagramming.
Commander Denniston could have told all this to Gill and Trevor-Roper, but he did not. Colonel Simpson, as the former head of the British Army’s wartime equivalent of Room 40, could certainly have explained it to Captain Robertson, except that the previous month he had been transferred out of MI5 to General Wavell’s army in the Middle East.9 Neither the Radio Security Service nor MI5 — as far as available documents show — were ever directly told that the ciphers of the type used by the Abwehr messages being intercepted had been compromised for years.
Probably to Denniston’s complete surprise, with Hitler’s invasion of Norway it was found that the Theseus was using these same simple ciphers to relay back to Germany the reports of spies on shore. Some of these deciphered messages were given to Churchill, again head of the Admiralty, and it undoubtedly caused him to remember the glory days of Room 40 when the signals of the German High Sea Fleet were being read. He ordered that the Theseus not be disturbed. When it was all over, and Norway lost, Gill again urged Strachey to get busy on the traffic that still was coming in from spies across the Channel, evidently in France, Belgium, and Holland. Strachey’s output was so meagre, however, that Gill offered him one of his own staff to help move things along.10
Meanwhile, MI6’s clandestine wireless service was coming of age. Its chief, Gambier-Parry, had been the marketing manager in Britain for the American radio and appliance maker Philco, and had recruited from the company a wireless engineer by the name of Harold Robin who developed a portable transmitter that weighed less than ten pounds. This, plus the introduction of super-secure one-time pads for enciphering messages, enabled MI6 to begin to deploy its own clandestine wireless observers in the field, rather than just in embassies, one such team reporting from a mountainside during the Norway crisis. This was a milestone in the modernization of MI6.11
Gambier-Parry’s operational headquarters was in Bletchley Park, a stately property MI6 acquired near the start of the war to house the expanding Government Code & Cipher School. He hired experienced signals personnel co-opted from the army and navy, and growth was so rapid that before long the team had to be moved to new premises five miles away at Whaddon
The decrypts ignited a blaze of publicity when the case was heard in The Hague in 1927. The German government may have had its suspicions, but it had no idea of the extent to which the British had been reading its secret communications, and probably still were. The immediate and lasting consequence was the Government Code & Cipher School was locked out of all German Foreign Office and German army traffic, the Foreign Office switching to unbreakable one-time pads (single-use sheets of random letters whose numerical equivalents are added to those of the letters in a message to encipher it) and the army to high-security plug board ciphering machines (akin to early telephone switchboards, they allow for the creation of thousands of unique electronic circuits).8 It stood to reason that the Abwehr, the German army’s secret intelligence service, would have taken similar measures.
To make the breach in secrecy even worse — and it could hardly have been — the types of German ciphers compromised were subsequently described by the American cryptologist Herbert Yardley in the popular book The American Black Chamber (1931) and in detail by Helen Fouché Gaines in her Elementary Cryptanalysis (1939). The most vulnerable had been transposition ciphers, which at their weakest were solvable by anagramming.
Commander Denniston could have told all this to Gill and Trevor-Roper, but he did not. Colonel Simpson, as the former head of the British Army’s wartime equivalent of Room 40, could certainly have explained it to Captain Robertson, except that the previous month he had been transferred out of MI5 to General Wavell’s army in the Middle East.9 Neither the Radio Security Service nor MI5 — as far as available documents show — were ever directly told that the ciphers of the type used by the Abwehr messages being intercepted had been compromised for years.
Probably to Denniston’s complete surprise, with Hitler’s invasion of Norway it was found that the Theseus was using these same simple ciphers to relay back to Germany the reports of spies on shore. Some of these deciphered messages were given to Churchill, again head of the Admiralty, and it undoubtedly caused him to remember the glory days of Room 40 when the signals of the German High Sea Fleet were being read. He ordered that the Theseus not be disturbed. When it was all over, and Norway lost, Gill again urged Strachey to get busy on the traffic that still was coming in from spies across the Channel, evidently in France, Belgium, and Holland. Strachey’s output was so meagre, however, that Gill offered him one of his own staff to help move things along.10
Meanwhile, MI6’s clandestine wireless service was coming of age. Its chief, Gambier-Parry, had been the marketing manager in Britain for the American radio and appliance maker Philco, and had recruited from the company a wireless engineer by the name of Harold Robin who developed a portable transmitter that weighed less than ten pounds. This, plus the introduction of super-secure one-time pads for enciphering messages, enabled MI6 to begin to deploy its own clandestine wireless observers in the field, rather than just in embassies, one such team reporting from a mountainside during the Norway crisis. This was a milestone in the modernization of MI6.11
Gambier-Parry’s operational headquarters was in Bletchley Park, a stately property MI6 acquired near the start of the war to house the expanding Government Code & Cipher School. He hired experienced signals personnel co-opted from the army and navy, and growth was so rapid that before long the team had to be moved to new premises five miles away at Whaddon
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