Answer
Harold Macmillan, Then British Prime Minister, exonerated Philby publicly in 1955. This came after Philby had been exposed as a Soviet double agent by two British intelligence defectors, Guy Burgess and Donald Maclean, who fled to the Soviet Union in 1951. Despite the defections, Macmillan downplayed the seriousness of Philby's espionage, calling it a "mischievous boy" act and declaring that he had "nothing to hide."