John Cairncross

Cairncross was born at Pine Cottage, Lesmahagow, in Lanarkshire, the youngest of four girls and four boys, of Elizabeth Andrew Wishart (1875–1958), a primary schoolteacher, and Alexander Kirkland Cairncross (1865–1947), an ironmongery manager.

His three brothers became professors, one of whom was the economist Sir Alexander Kirkland Cairncross (a.k.a. Alec Cairncross).

The journalist Frances Cairncross is his niece.

John Cairncross (25 July 1913 – 8 October 1995) was a British civil servant who became an intelligence officer and spy during the Second World War.

As a Soviet double agent, he passed to the Soviet Union the raw Tunny decryptions that influenced the Battle of Kursk.

He was alleged to be the fifth member of the Cambridge Five.

He was also notable as a translator, literary scholar and writer of non-fiction.

The most significant aspect of his work was helping the Soviets defeat the Germans in major World War II battles; he may also have told Moscow that the US was developing a nuclear bomb.

Cairncross grew up in Lesmahagow, a small town on the edge of moorland, near Lanark in the Central Belt of Scotland, and was educated at Lesmahagow Higher Grade School (where his name appears as the 1928 winner of the Dux prize); Hamilton Academy; the University of Glasgow; the Sorbonne; and Trinity College, Cambridge, where he studied French and German.

After graduating, Cairncross took the British Civil Service exam and won first place in both the "home civil service" and the "foreign office and diplomatic service" competitions.

An article in the Glasgow Herald on 29 September 1936 noted that Cairncross had scored an "outstanding double success of being placed 1st in the Home List and 1st in the competition for the Foreign Office and the Diplomatic Service," and that he had been placed fifth in the University of Glasgow bursary competition of 1930, and was also a Scholar and Bell Exhibitioner at Trinity College, Cambridge.

Cairncross worked initially in the Foreign Office before transferring to the Treasury and then the Cabinet Office, where he worked as a private secretary to Lord Hankey, the Chancellor of the Duchy of Lancaster.

It has been suggested that in 1936, whilst at Cambridge, Cairncross joined the Communist Party of Great Britain, but he was not noted whilst at university for any political activity by his brother Alec, who was also at Cambridge until 1935.

Sir Alec also recalled that John "was a prickly young man, who was difficult to argue with and resented things rather easily".

It was while he was working with the Foreign Service (circa 1936) that he was recruited as a spy for the Soviets by James Klugmann of the Communist Party of Great Britain.

In 1942 and 1943 Cairncross worked at GC&CS, Bletchley Park in Hut 3, on ULTRA ciphers.

He had access to communications of the German military and intelligence services.

From 1942 onwards, the German High Command communicated with Army group commanders in the field using a machine that the British codenamed Tunny.

Cairncross smuggled Tunny decrypts due to be destroyed out of Hut 3 in his trousers, transferring them to his bag at the railway station before going to meet his NKVD contact in London, Anatoli Gorsky.

The Soviets were particularly interested in traffic between Berlin-Pskov, Berlin-Helsinki, Berlin-Lisbon, Trebizond-Istanbul, Berlin-Bucharest, and Kirkenes-Oslo.

They were also interested in British efforts to decipher Soviet ciphers and in the joint effort by German and Japanese cipher experts to decipher Soviet signals including military ones, which the combined German-Japanese effort failed to achieve with the Soviet diplomatic ciphers.

The raw transcripts decrypted by Colossus were passed to intelligence officers at Bletchley Park, who created reports based on this material by disguising its origin as signals traffic.

By providing verbatim transcripts, Cairncross showed the Soviets that the British were breaking German ciphers.

It was then considered to be in the British interest for the Soviet Union to be made aware of German military plans, but not of how they were obtained, because of "defective and leaky" internal security in the Soviet Union.

The Lubianka originally suspected a "trap" because of the amount of high-grade material supplied, but it was acted on and found to be accurate.

One item passed was "advance warning to develop tanks with stronger shells in the light of German armament reports. Information based on decrypts was passed to the Soviets through official channels as from Agent "Boniface". However, Stalin distrusted unsourced intelligence presented to him by Britain and the United States.

Operation Citadel was the codename given by Nazi Germany to their offensive which led to the Battle of Kursk.

After being defeated at Kursk, the Wehrmacht retreated steadily until Berlin was taken.

Tunny decrypts (transcripts) gave the British advance intelligence about Operation Citadel whilst it was being planned.

In June 1943, he left Bletchley Park for a job in MI6.

Cairncross passed decrypted documents through secret channels to the Soviet Union.

Codenamed Liszt by the Russians because of his love of music, Cairncross had been instructed to get into Bletchley Park, known to the KGB as Kurort.

Almost all raw transcripts were destroyed at the end of the war but a surviving transcript dated 25 April 1943 from German Army Group South signed by Maximilian von Weichs shows the high level of detail available to British intelligence officers.

Analysts deduced the northern and southern attack routes, and a report based on this transcript was passed through official channels to Stalin.

During this period, Cairncross provided a second clandestine channel, supplying raw Tunny transcripts directly.

Axis occupation forces in Yugoslavia used radio communication extensively.

Cairncross confessed in secret to MI5's Arthur S. Martin in 1964 and gave a limited confession to two journalists from The Sunday Times in December 1979.

He was given immunity from prosecution.

According to The Washington Post, the suggestion that John Cairncross was the "fifth man" of the Cambridge ring was not confirmed until 1990, by Soviet double-agent Oleg Gordievsky.

This was re-confirmed by former KGB agent Yuri Modin's book published in 1994: My Five Cambridge Friends Burgess, Maclean, Philby, Blunt, and Cairncross by Their KGB Controller.