People have been writing about Harold "Kim" Philby for decades.

The legendary Soviet spy led a double life while he worked his way up the ranks of British intelligence, all the while passing on secrets to his handlers before his eventual defection to Moscow.

But a new book by Cambridge University historian Christopher Andrew reveals further details about Philby's role as a high-level Soviet messenger and how he reacted to the post-war defection of a Soviet cipher clerk to Canada in the fall of 1945.

In "The Defence of the Realm," Andrew writes the first official history of Britain's domestic spy service. It's the first time that an independent historian has been given access to the Security Services' archives and the book provides an in-depth look at the first 100 years of MI5, from 1909 to the present.

One chapter of the book is devoted to the post-war defection of Soviet cipher clerk Igor Gouzenko in Ottawa and the proof of a spy-ring that existed under the nose of the Canadian government.

The defection

Sixty-four years ago this past September, Gouzenko strode out of the Soviet Embassy in Ottawa with documents stuffed under his shirt.

The 26-year-old worked for a branch of Soviet intelligence and he wanted to defect.

It was a risky move. The previous month, another Soviet spy named Konstantin Dmitrievich Volkov had tried the same move in Turkey. He got caught and was taken back to Moscow and executed.

In Canada's capital city, Gouzenko first went to the Ministry of Justice and the Ottawa Journal for help. But his first attempt was not successful, as nobody at the newspaper or in the government could help him that night. Or the next night.

Soon enough, Gouzenko managed to defect and he brought proof of a Soviet spy-ring that had wormed its way into many levels of the Canadian government, as well as the country's scientific research community.

Looking back, Andrew writes that the now-defunct Journal -- which ceased production in 1980 -- missed out "on the spy exclusive of the decade" the day Gouzenko walked in its doors. The defection wouldn't even be public knowledge until the following February.

The fallout

The Gouzenko Affair, as it has come to be known, was a defining event in the ensuing Cold War and sent shockwaves throughout Ottawa and London.

"I think it's one of the great stories in Canadian history, but it's not much known in detail (to the public)," said Wesley Wark, a University of Toronto intelligence historian who spoke with CTV.ca by telephone earlier this week.

Canada's prime minister at the time, William Lyon Mackenzie King, wrote about the discovery of the spy-ring in his own diary.

"During the period of war, while Canada has been helping Russia and doing all we can to foment Canadian-Russian friendship, there has been one branch of the Russian service that has been spying on [us] ... The amazing thing is how many contacts have been successfully made with people in key positions in government and industrial circles," Mackenzie King wrote, as quoted in Andrew's book.

At the time of the Gouzenko defection, Philby worked for Britain's Secret Intelligence Service -- the foreign spy service, also known as MI6 -- but he headed Section IX, which handled all Soviet and Communist counter-intelligence. He also had responsibilities liaising with American and British intelligence contacts.

That left Philby -- again, a Soviet agent -- in good position to pass on information.

"He was a very, very important Soviet source," Wark said.

But despite Philby's considerable connections, Wark said the Soviet spy couldn't shut down what was coming out of Ottawa, following the Gouzenko defection.

"He couldn't control it, he couldn't stop the leaking, Soviet intelligence decided they couldn't do anything about it, so it rolled on," Wark said.

"The real source of delay in all of this was really Mackenzie King who was determined not to make this a public affair, who was determined to avoid any kind of friction with the Soviet Union if he could help it, and wanted to push the British and American allies out front so Canada could kind of shelter behind their greater power and their intelligence communities."

But that didn't mean that Philby hadn't been successful in quashing other secrets on other occasions. It was he who passed on the tip about the Soviet spy who wanted to defect in Turkey, a connection that could have exposed Philby himself.

Spies in Canada

The papers that Gouzenko brought forward specifically showed that the Soviet Union had spies active in Canada and helped to identify who some of them were.

One of those spies was Alan Nunn May, a British scientist who was on the prowl for nuclear secrets during the latter-half of the Second World War.

Nunn May found work at a nuclear research laboratory in Montreal, where he had been since 1943. And days after Hiroshima happened, he managed to sneak samples of radioactive Uranium over to his Russian handlers.

According to Andrew's book, Gouzenko's information showed that Nunn May was supposed to have a meeting with his Soviet handlers outside the British Museum in London on Oct. 8.

The information was detailed enough to know that Nunn May was supposed to carry a copy of The Times under his left arm, so that his Soviet contacts would know who he was.

Philby promptly passed this information on to Moscow and Nunn May never showed up where he was supposed to, even while MI5 kept him under surveillance.

"According to MI5, May has not put a foot wrong from the time he arrived in England. He did not establish any suspicious contacts. He does not show any signs of being afraid or worried and continues to work quite normally on his academic research," Philby wrote to one of his Soviet superiors, weeks later on Nov. 18.

But Wark belives that Nunn May missed the meeting on his own accord, sensing trouble in the undercover waters in which he swam.

The Gouzenko story was too big at that time, Wark said, and Moscow didn't want to expose the most senior people -- like Philby -- that it had undercover.

"Alan Nunn May didn't make his meeting because he chose not to make his meeting," Wark said. "Nunn May was already beginning to, kind of, feel shadows collecting around him and he was just being ultra-cautious. It was his own decision, it was not a decision that was relayed to him by anybody in Soviet authority. It just didn't work out that way."

Nunn May wouldn't be arrested for several months after that point. On May 1, 1946, the outed spy was convicted of violating the Official Secrets Act. He received a 10-year prison sentence, but was paroled at the end of 1952.