At 6pm on April 6 1954, Robert Maxwell strode into the Plaza, a luxury hotel off Central Park in New York, on one of his frenetic business trips.
A dashing young man, 6ft tall, he oozed the image of one forever shuttling between countries on his way to fame and fortune. The Daily Express had recently pronounced him "one of the most remarkable men" in the publishing trade, running two big companies at 30. "Not bad going," it wrote.
Maxwell was deeply ambitious and intent on transforming the boy born into rural poverty in Czechoslovakia into a great man of international business and world affairs.
The pension scandal which was to make his name a byword for corruption was far in the future.
But, as he checked into his hotel that April evening, little did he know he was being kept under intense surveillance by the Federal Bureau of Investigation (FBI), which suspected that he was a Soviet spy. In the middle of the cold war, the FBI had enormous resources to watch any "reds".
The director of the FBI, J Edgar Hoover, had ordered an investigation into Maxwell in 1953. Now 631 pages of the FBI files released to the Guardian under the United States Freedom of Information laws reveal that this was the start of an eight-year investigation. What triggered it has been excised from the file.
Even before he checked in to the hotel, an informant "of unknown reliability who is familiar with the activities in the Plaza hotel" had told the FBI that Maxwell had reserved a room, and that he had also stayed at the hotel in February.
Another informant, this time of "known reliability", logged every conversation with a succession of visitors and each telephone call, along with the subjects discussed and the language spoken.
The informant, whose name is blanked out, "stated that at 6.15pm, Maxwell was visited by an unknown male individual, and they were overheard by [blank] to discuss the publishing and book business. Throughout the conversation by the unknown individual and Maxwell, it was indicated that the unknown individual was... under Maxwell's supervision and jurisdiction."
The informant "stated Maxwell has a very deep voice, uses excellent diction and has a pronounced British accent". The FBI, chronicling all his comings and goings, and those of his visitors, even noted that Maxwell "has been observed to wear a black homburg hat in past" and that "[blank] declared that at 10.30pm, Maxwell watched the Edward R Murrow program, which concerned Senator Joseph McCarthy's answer to Murrow regarding communist sympathies."
Given the scope of the surveillance, the mystery informant appears to have been a member of the hotel staff lurking outside Maxwell's suite.
The FBI's interest had been aroused because of Maxwell's publishing contacts with American nuclear scientists in secret research centres.
Even after Maxwell left the hotel at 10.30am the following day, the FBI kept tabs on him. "[Blank] observed Maxwell enter a black 1947 or 1948 Buick with New Jersey license plate, which the unknown male who had carried Maxwell's baggage was driving." They were tailed to the airport, and the Buick and its driver were checked.
In a "lengthy and extensive investigation" over eight years, the FBI agents kept a close watch on Maxwell whenever he visited the US. Airport staff were ordered to tip off the bureau as soon as he touched down. The G-men scrutinised anyone he met.
According to the released records, the FBI's inquiries ended in 1961, because the bureau had failed to uncover any connection between Maxwell and Soviet spies. But it seems Maxwell hoodwinked them.
It appears that, ever the opportunist in search of profit, Maxwell cooperated with both the KGB and Britain's foreign spying agency, MI6.
For years, Maxwell was accorded favoured status in the Soviet Union as he frequently travelled back and forth through the Iron Curtain. From the late 1940s, he was in regular contact with Soviet leaders and the KGB.
He was secretly paid by the KGB to publish 50,000 copies of a series of fawning biographies of communist leaders, although he duped them about the number that were actually printed.
In the mid-1950s, he had begun to translate and publish the work of Soviet scientists in journals which were sold to libraries and research institutions throughout the west. The Soviets had given him exclusive rights and he made millions.
But ironically, it was MI6 which had given him the money to establish himself in publishing. MI6 had bankrolled him in the early 1950s as they believed it would be a good chance to obtain intelligence about Soviet scientific work.
Maxwell's side of the bargain was to pass on information and help MI6 contact and recruit scientists.