As a double agent, he not only betrayed his home country, but the American cousins who placed so much trust in their more experienced British counterparts. That is why I have written a biography of Angleton - not only to capture Kim Philby through American eyes, but to understand the impact his audacious treachery had on the CIA in its formative years.

Along the way, Philby touched on homoerotic currents as electric and buried as the phone lines those spies routinely wiretapped. His betrayal of Angleton was ideological and emotional. Its impact was political and psychological.

These were times fraught with sexual tension in intelligence agencies, on both sides of the Atlantic.

Philby and Angleton’s friendship blossomed in the spring of 1950, amid a moral panic in Washington. In a series of sensational speeches, Republican Senator Joe McCarthy had woven together the threats of communism and homosexuality into twin fervors that historians have dubbed the ‘Red Scare’ and the ‘Lavender Scare’.

The two spies were cosmopolitan men, who disliked McCarthy’s demagogic style. Angleton was married and a father of three. Philby was on the second of his four marriages, had four children, several mistresses, and many conquests, not all of them female. His housemate in Washington (and fellow spy) was Guy Burgess, a Cambridge classmate who had previously worked for the BBC and the Home Office. Openly gay, he did not conceal his amused contempt for American morality.