The RAF's secret spies: Declassified CIA documents reveal British pilots flew U2 missions over Soviet Union during the Cold War British pilots were involved in the U-2 flights in 1959 and 1960 They were used in sensitive missions after an agreement between the CIA and the head of MI6, who saw intelligence benefits for Britain By Guy Walters RAF officers flew spying missions over the Soviet Union at the height of the Cold War, it was revealed yesterday. After decades of secrecy, the CIA declassified documents that show British pilots were involved in the U-2 flights in 1959 and 1960. They gathered vital intelligence which the head of the American agency said he regarded as worth "a million dollars." Classified: A U-2 plane successor to those flown in the Cold War Until now the Ministry of Defence has neither confirmed nor denied the participation of the RAF in the controversial missions, a position it will no longer be able to maintain. The first U-2 flights over the Soviet Union started in July 1956, but despite the valuable information gathered, President Dwight Eisenhower was concerned about the ramifications of such a flagrant breach of Russian air space if they were discovered. Unfortunately for the Americans, even though the hi-tech U-2s flew at more than 70,000ft, the Russians were able to track the planes. Shot down: Pilot Gary Powers was captured in 1960 in the Soviet Union The Soviets sent a strongly-worded protest to Eisenhower, who developed cold feet about the missions and suspended such flights in December 1956. However, the CIA was very keen for the spying missions to continue and looked for ways, in the words of the newly released document, "to increase the possibility of plausible denial." The solution was to use British pilots for the sensitive missions. During the spring of 1957, negotiations took place between the CIA and the chief of MI6, Sir Dick White, who saw the obvious intelligence benefits for Britain. By the summer of 1958, Prime Minister Harold Macmillan had given his authorisation, and four RAF officers, Squadron Leader Christopher Walker and Flight Lieutenants Michael Bradley, John MacArthur and David Dowling - all of whom were in their twenties and single - were sent to train in Texas. But flying the U-2s was not without risk, and on July 8, 1958, Walker was killed when his plane crashed. The cause was never definitively established, but it is thought the aircraft disintegrated at high altitude. He was immediately replaced by Wing Commander Robert "Robbie" Robinson. By January 1959 all four men had finished their training and were sent to a secret air base in Turkey, from where they would launch their flights over the Soviet Union and the Middle East. In order to emphasise American denials of the operation, the U-2 planes were formally transferred on paper to the British government. Eisenhower wrote a top-secret letter to Macmillan stating: "British missions are carried out on your authority and are your responsibility." And the flights remained a secret in Britain, too. The pilots were no longer paid by the RAF, but by MI6, and the public was told the men were engaging in "high-altitude weather-sampling missions." The first mission was flown by Robbie Robinson on December 6, 1959, over the Kapustin Yar missile test range and a squadron of long-range bombers in the Ukraine. Sensitive missions: Until now the Ministry of Defence has neither confirmed nor denied the participation of the RAF It was a huge success and proved the Soviets did not have as many bombers as they claimed - a vital piece of intelligence at the height of the Cold War. The head of the CIA called Robinson's bomber picture "a million-dollar photo." The second British U-2 mission over the Soviet Union was flown by John MacArthur the following month. Although his brief was to look for missile sites around the Aral Sea, he ended up uncovering a new type of Soviet bomber called the Tupolev Tu-22 at Kazan. The Americans later resumed their involvement in the U-2 missions, but this came to an abrupt end in the wake of the Soviets shooting down and imprisoning US pilot Gary Powers in May 1960. The British ordered the RAF officers to leave Turkey immediately. The following year, all four British pilots received the Air Force Cross, although their citations in the London Gazette did not mention exactly why. Only now, after more than 50 years, has the truth been revealed.