Born in London, England in 1913, the son of Sir Donald Maclean, a noted attorney and Scottish politician. Sir Donald served as a member of Parliament and was knighted in 1917.

Was educated at Gresham and then moved on to Cambridge where he counted within his circle of friends, Anthony Blunt, Guy Burgess and Kim Philby. Was influenced greatly by leftist teachings and believed early on in the cause of communism. Was introduced, while at Cambridge, to a Soviet controller who recruited him into the service of the Soviet Union. Was convinced to disassociate himself from active communist party membership and activity so as not to draw undo attention to himself.

Graduated from Cambridge in 1934 and immediately gained a position in the Foreign Service (despite having acknowledged having had leftist leaning while in school). Through contacts loyal to his father, Maclean moved his way up though the ranks of the Foreign Service, attaining a level where he was privy to classified information. Passed this information to his Soviet handler.

Was assigned to the Foreign Office Central Department, responsible for Germany, Belgium and France and was assigned to an office in Paris in 1938. Met Melinda Marling, the daughter of an American oil executive, while in Paris and the couple married in 1940 but immediately fled the country due to Nazi occupation. After working for the foreign office for nine years, Maclean was appointed the first secretary for the British Embassy in Washington, DC. He also served as the head of chancery on occasion making him privy to even more information as all material delivered to the British ambassador was easily within his reach. After having a child, Melinda moved to the United States, living in New York with her mother. Donald routinely visited New York City on weekends, ostensibly to visit his wife, but also to pass information to his New York based Soviet contact.

Served as Britain’s secretary on the Combined Policy Committee, gaining access to classified information about British and American plans regarding atomic energy and nuclear weaponry. He was also given access to information from the United States Atomic Energy Commission. Worked alongside Alger Hiss, a U.S. State Department official regarding plans for the United Nations. Discussed U.S. policy on a number of topics, including U.S. Military participation in South Korea.

Continued his trips to New York, unaware that passages in the Venona documents described a Soviet spy who also visited New York at the same time (in July 1946).

The documents were transmitted accidentally with a lower security encryption and included information from transmissions between British Prime Minister Winston Churchill and U.S. President Harry Truman, including specific serial numbers for those transmission. The serial numbers helped to narrow down the number of people who would have had access to the documents. This information, in addition to his constant requests to participate in meetings of the Atomic Energy Commission led the CIA to maintain surveillance of him.

James Angleton, head of the CIA’s counter-intelligence program, determined that Maclean was indeed a Soviet spy and caused his pass to the Atomic Energy Commission to be revoked. Angleton informed MI5 of his suspicions and Kim Philby was apprised of the situation. Philby warned Soviet officials and they informed Maclean of the situation.

Maclean, a known bi-sexual, was observed in drunken stupors, prowling for homosexual liaisons. His drinking grew to a dangerous level until he was recalled by the British government and returned home in 1948. He was transferred to Cairo, Egypt where he served as chancery for the British Embassy but again suffered from drunken episodes and was again recalled to London in 1950. Nonetheless, in early 1951 he was assigned a new position, this time as head of the American Department of the Foreign Office.

Maclean’s drinking became problematic once again as he vociferously denounced the capitalism of the west and espoused the virtues of communism during dinner parties and formal affairs. Word of his behavior circulated around London and in January 1951, Kim Philby learned more about the information in the Venona documents and worried that he was in impending jeopardy of being arrested. Concerned that telephone calls or cables to London might be intercepted, Philby sought another way to warn Maclean. Guy Burgess, also enjoying a reputation as a drunkard, engaged in sufficient misbehavior to merit being sent home from the United States where he was serving with the British embassy. Burgess immediately informed Anthony Blunt of Maclean’s impending danger and Blunt likewise informed their Soviet handler Yuri Modin.

Modin immediately set into motion an escape plan and three days before Maclean was to be arrested by MI5, Burgess drove him to Southampton where the two climbed aboard a ferry boat, the S.S. Falaise that took them to St. Malo. Eventually the two made their way to Moscow where they hailed as heroes to the Soviet people. Maclean was given the rank of KGB Colonel. He was joined in September by his wife and children. Maclean and Burgess were put on display for the western press by the Soviet government in 1956. Maclean worked hard to adapt to the Soviet culture and was rewarded by the government with salary and accommodations.

He wrote several publications on economics and was published in the Soviet Union and Britain. In 1966, Melinda Maclean began an affair with Kim Philby, Philby having defected in early 1963. She moved in with him two years later but returned to the United States in 1979.

Donald Maclean died of a heart attack on March 6, 1983. His ashes were buried in England months later.