Walter Krivitsky and the Exposure of John Herbert King
By Harlan Pryce ·
A Foreign Office cypher clerk’s betrayal of British secrets was pinpointed by a Soviet spymaster who fled his own regime to warn the West—a breach that stayed in the shadows for years.
John Herbert King had the keys to the kingdom and sold them for a price the Soviet Union was happy to pay. As a Foreign Office cypher clerk who provided Foreign Office communications to the Soviet Union between 1935 and 1937, King did more than leak documents; he compromised the very language of British diplomacy, allowing Moscow to read the private thoughts of the British state in real time. He was eventually sentenced to ten years in prison as a spy in October 1939, but his capture was not the result of a sudden internal audit or a lucky break. It was the result of a high-level betrayal from within the Soviet military apparatus itself.
What we have here is a catalogue description of a personal file, a summary of a larger body of evidence that establishes the movements and the utility of a man who knew where the bodies were buried. The record, identified as KV 2/805, focuses on Walter Krivitsky, a Soviet military intelligence spymaster who defected to the West and revealed plans for the signing of the Molotov–Ribbentrop Pact. Krivitsky was a man who had climbed to the top of the Soviet military spy network in Western Europe before the Great Purge made his position untenable. He broke with the Soviet authorities in 1937 and fled to the USA, a move that turned him into one of the most dangerous witnesses the Kremlin ever produced.
London, 1940
By 1940, Krivitsky had moved from the safety of the Americas to the front lines of the intelligence war. The record establishes that he "was interviewed at length in London by MI5 officers in 1940," a series of encounters that resulted in "a wealth of reporting on Soviet Intelligence techniques and operations." These interviews were not mere debriefings; they were a mapping exercise. Krivitsky provided a "unique insight into the inner workings of Soviet Intelligence in the 1920s and 1930s," essentially handing the British a manual on how their own government was being hollowed out from the inside.
Among the most damning revelations was the identification of the human assets Moscow had placed in the heart of the British government. The record states explicitly that "KRIVITSKY's information led to the identification of at least one British spy," namely John Herbert King. The line between the defector and the clerk is direct and lethal. Krivitsky did not just describe how the Soviets operated; he named the men who were doing the operating. In the cold logic of espionage, Krivitsky traded King's freedom for his own continued utility to the West.
Inside the CPGB Pipeline
Krivitsky’s reporting went beyond individual traitors to expose a systemic infrastructure of betrayal. The record notes that of "particular interest is the involvement in espionage of local Communist Parties, especially the British Communist Party." The British Communist Party, the largest communist organisation in Britain, founded in 1920, had long presented itself as a political movement of the working class, but Krivitsky revealed it was functioning as a talent pool for Soviet Intelligence.
The connection is clear: Soviet Intelligence did not always need to recruit high-level ministers; they leveraged the existing ideological fervor of the CPGB to find people like King—individuals with access and a willingness to serve a higher cause. By using the party as a front, Moscow created a layer of deniability. If a party member was caught, the Soviet state could dismiss it as the act of an overzealous local amateur. However, Krivitsky’s reporting stripped away this veneer, showing that the CPGB was not merely a political ally but an active arm of the Soviet intelligence machinery.
This pattern of leveraging ideological fronts is a recurring theme in the archives. For instance, the record of Margherita Standen, a German national employed in the Soviet Trade Delegation in London during the 1930s (KV 2/4232), shows her on "close terms with a number of communists, some of whom had suspected espionage links." Standen's trajectory—moving permanently to the USA in 1939—mirrors the movement of intelligence data across the Atlantic. The Soviet Trade Delegation and the CPGB were not separate entities; they were the two halves of a pincer movement designed to infiltrate British society.
A Structural Failure
When one looks at the case of John Herbert King alongside other records, a disturbing pattern emerges. The record KV 2/1426 describes Igor Gouzenko, a Soviet Military Intelligence officer who worked as a cypher clerk in the Russian Embassy in Ottawa before defecting in 1945. Gouzenko, using the alias CORBY, provided a comprehensive account of Soviet activity that, like Krivitsky's, exposed the fragility of cypher security.
The coincidence of two high-profile breaches involving cypher clerks—King in London and Gouzenko in Ottawa—is not a coincidence. It points to a systemic vulnerability in how the West handled the people who encrypted and decrypted its most sensitive secrets. These were low-level employees with high-level access, individuals who were often overlooked by security services until a defector like Krivitsky or Gouzenko pointed a finger. The British state treated King as an isolated criminal, but the record suggests he was a symptom of a wider pathology.
The Desk's Reading
The desk's reading is that the focus on John Herbert King in this file serves as a convenient narrative shield. The record emphasizes the identification of "at least one British spy," a phrasing that is suspiciously minimal given Krivitsky's seniority and the depth of his knowledge. A man of Krivitsky's rank did not defect to reveal a single cypher clerk; he defected with a map of the entire Soviet network in Western Europe. If this file is shaped the way it looks, the emphasis on King was intended to satisfy the need for a public arrest while masking the identification of higher-ranking officials whose exposure would have caused a political catastrophe in London.
Furthermore, the timeline of Krivitsky’s movements suggests a coordinated Anglo-American effort to synchronize Soviet intelligence data prior to the full wartime alliance. Moving from the USA in 1937 to MI5 interviews in 1940 indicates that Krivitsky was a shared asset, a bridge used to align the security apparatuses of two powers who didn't yet fully trust each other, but both feared the Kremlin. The pattern suggests that the British Communist Party was highlighted as the primary espionage conduit to divert attention from "non-party" assets—the professional sleepers and the high-society moles who did not carry party cards but were far more damaging than any cypher clerk.
What a full release of the KV 2/805 file would likely show is a list of names that never made it to a courtroom. The withheld pages are protecting the ghosts of the British establishment—the men who were identified by Krivitsky but were too well-connected to be prosecuted. The state preferred a ten-year sentence for a clerk over a systemic purge of its own elite. The cost of this preference was a blindness that lasted for decades, a failure to realize that the breach was not in the cyphers, but in the culture of the people who held them.