*Mild spoilers for season 3 of The Crown on Netflix ahead.
Viewers of the third season of The Crown on Netflix will likely have their curiosity piqued by Anthony Blunt, the art historian who is revealed to be a spy for the Russians during his 19 years of service to the Queen at Buckingham Palace. Instead of getting the boot once he was discovered, however, Blunt went on to remain under Her Majesty's employ for eight more years—until his official retirement. While treason never looks good on a resume, the royal class had good reason to keep him on.
Blunt, who was born and raised in England, visited the Soviet Union in 1933 and was indoctrinated as a spy after being convinced of the benefits of Communism in fighting fascism. He began recruiting his university classmates at Cambridge before serving during World War II and leaking information about the Germans to the KGB. Blunt was one of five Cambridge graduates under Soviet direction. Two of them, diplomats Donald Maclean and Guy Burgess, relocated to the Soviet Union in 1951. Another, Kim Philby, went undetected until 1961. John Cairncross escaped notice, too, but was eventually outed.
However, it was Blunt who had a post at Buckingham Palace. After being tipped off by American intelligence, MI5 interrogated Blunt. He confessed to his treachery in 1964 and was granted immunity from prosecution. Why was he able to remain employed? One theory has it that British intelligence was so embarrassed by Blunt's ability to circulate in the upper levels of the monarchy that firing him would have raised too many questions. Another thought has Blunt having knowledge of some bizarrely congenial wartime correspondence between Adolf Hitler and the Duke of Windsor (a.k.a. King Edward VIII, whose abdication led to Elizabeth's eventual ascension to the throne).
Whatever the case, the Queen was advised by MI5 to keep Blunt around. In his role as art curator, he had no access to classified information. Blunt was at the Palace through 1972 and spent another seven years roaming London giving lectures. His actions remained a tightly guarded secret until Margaret Thatcher disclosed his treason in 1979.
As for that speech seen in The Crown, where Olivia Colman's Queen Elizabeth makes some not-so-subtle digs at Blunt at the opening of a new exhibition, there's no record of such a takedown ever happening. While the two reportedly kept their distance from each other in private, according to Miranda Carter's Anthony Blunt: His Lives:
“Blunt continued to meet the Queen at official events. She came to the opening of the Courtauld’s new galleries in 1968, and in 1972 she personally congratulated Blunt on his retirement, when the Lord Chamberlain, knowing nothing of his disgrace, offered him the honorary post of Adviser on the Queen’s pictures—inadvertently continuing his association with the Palace for another six years.”
Stripped of his knighthood as a result of the truth about his actions being made known, Blunt became a recluse and died of a heart attack in 1983. His memoirs, which were made public by the British Library in 2009, indicated his regret, calling his spy work "the biggest mistake of my life."