The James Bond author Ian Fleming rescued MI6 from an untimely death that would have put paid to his 007 hero before he was even created.

But in saving the service, newly released secret documents reveal, Fleming inadvertently helped pave the way for the Secret Intelligence Service (MI6) to be infiltrated by members of the Cambridge spy ring, its most destructive traitors.

Fleming was an officer in the navy’s intelligence department during the second world war. The secret files, released after more than 60 years, reveal that he was the navy’s liaison officer with MI6, which gave him valuable background knowledge for his Bond books.

Within a few months of the outbreak of war, naval chiefs were so angry that an army officer had been put in charge of MI6, which had traditionally been led by a navy officer, that they lobbied Winston Churchill to let them start their own rival espionage service.

The documents show Fleming steered them away from the idea, warning that if MI6 were downgraded there was “a grave danger of letting the baby out with the bath water”.

His suggestion, dated April 1940, that they should instead insert some “new blood” into MI6 to change it from within was accepted by naval chiefs.

In Fleming’s fiction, Bond was one of those recruits. The novel You Only Live Twice, in which 007 is “killed off”, features an obituary that says he joined MI6 in 1941.

In reality, however, the desire for “new blood” led to the recruitment of Kim Philby in June-July 1940 and John Cairncross, two members of the KGB’s Cambridge ring who wreaked havoc in MI6 during the early part of the cold war.

The naval intelligence file on the Secret Intelligence Service has only recently been released to the National Archives at Kew, southwest London. It was discovered by Phil Tomaselli, an intelligence writer working on a guide for people who want to track down evidence of their relations working as spies.

The first “chief” of the British secret service was a naval commander, Mansfield Smith-Cumming. He was known simply as “C”, a title that has been handed on to all future chiefs and inspired Fleming’s fictional “M”.

Cumming’s successor was also a naval officer, Admiral Sir Hugh “Quex” Sinclair, and as a result the navy grew accustomed to being able to go straight to the chief of the secret service to get what it wanted.

When Sinclair died in November 1939, his deputy, Colonel Stewart Menzies, was put in charge, alarming the naval chiefs. Underfunding in the 1930s had already led to dissatisfaction in the navy over the standard of intelligence provided by MI6.

One member of naval intelligence quoted in the file said the MI6 reports sent to the navy were “almost without exception worthless, and not infrequently so evidently worthless as to provoke immediate laughter”.

Fleming had been recruited at the start of the war as personal assistant to Rear Admiral John Godfrey, director of naval intelligence.

Godfrey put great store by Fleming’s advice, later saying it would have been better if Fleming had been the director of naval intelligence and he had been Fleming’s assistant.

He put him in charge of liaison with MI6 but, at the same time, he began lobbying for a separate naval secret service.

The head of the navy, Admiral Sir Dudley Pound, agreed with Godfrey’s claim that the navy was “not getting the information we need and there is little likelihood that under the present organisation that we shall”.

Pound told Churchill, then first lord of the Admiralty, that the navy should be allowed to choose its own man to be deputy chief of MI6 for a six-month trial period.

If that did not improve things, says a document in the file, “then we should set up a separate organisation and the deputy director would have the necessary knowledge to do this”.

Churchill promised to discuss the issue with Menzies, the new chief of MI6, but told Pound the plans for a separate naval secret service should be put on hold until the completion of a review into the whole of British intelligence.

When that report largely exonerated MI6 of any failings, senior naval officers denounced it as a whitewash and renewed lobbying for their own service.

Fleming, who went on to become foreign manager of The Sunday Times, successfully intervened with Godfrey and the naval bosses on behalf of MI6. “I think that the infusion of new blood into the existing organisation would be better than chopping off hoary but experienced heads,” he said.

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