The existence of a tape recording of Harold Macmillan and Bob Boothby discussing Boothby's affair with Macmillan's wife, Lady Dorothy, has been disclosed by a former Conservative MP.
The tape recording was made accidentally by Boothby's wife. In it, the former prime minister and her husband discuss Lady Dorothy Macmillan, who had a child by Boothby.
Macmillan, later awarded a peerage by Baroness Thatcher, describes in the recording how he destroyed Boothby's love letters to his wife after her death. Its existence was uncovered by Robert Rhodes James, the former MP for Cambridge and a distinguished writer, when he was researching for his biography of Boothby.
"I have heard the recording and it's rather an eerie thing. Macmillan describes how he destroyed Bob's letters to Dorothy," Mr Rhodes James says in a BBC 2 documentary on the Macmillans' marriage, which was torn by the affair.
"He had an outside incinerator and he didn't know how to work it. He piled all the letters in the incinerator and the wind got up. Suddenly, the letters were flying all round the garden, and he was chasing them," Mr Rhodes James said.
"One has this picture of this retired statesman rushing around and trying to capture and burn the letters of his wife's lover."
Macmillan's last words on the tape were "And so it all ended ..." Boothby then added: "And so it ended." Macmillan outlived Lady Dorothy, who was the daughter of the Duke of Devonshire, by 20 years.
The programme, which is part of a series called Reputations, argues that the former prime minister's personal unhappiness at being cuckolded by Boothby, to whom he gave a peerage when he was in office, greatly intensified his political ambitions.
It suggests he might never have risen to the leadership if the affair had not happened. The programme also portrays Macmillan as a scheming liar when he prevented Rab Butler from winning the Tory party leadership. The picture is at odds with his affable "never-had-it-so-good" image.