She died last week aged 80 and Lord Denning, aged 94, spoke publicly for the first time about the 'headless man' - an unidentified naked man photographed in a compromising position with Margaret Argyll. The photographs were used by the Duke of Argyll in the bitter divorce action against his wife.
In her autobiography, Forget Not, the Duchess says she agreed to see Lord Denning on condition that he came to her house. She wouldn't join the queues of people being seen entering his chambers.
Nowadays Lord Denning is rather deaf. But his mind is alert. At his home at Whitchurch, in Hampshire, he explained how he had been able to identify the headless man. He refused to say who he was but left little doubt about his identity.
I imagine that when the Hollywood actor Douglas Fairbanks Jnr called on Lord Denning in the summer of 1963 he had no idea he would be identified as the 'headless man', a fact that remained secret until the duchess's death.
The photographs, two polaroid snaps, were of the Duchess, naked but for a pearl necklace posing for the camera with her nude companion, whose head was not in the picture, and another of her performing oral sex.
Speaking from New York last week, Mr Fairbanks, 84, refused to confirm or deny he was the 'man without a head'. 'This is not a court of law and I don't talk about things like that,' he told the Independent on Sunday. It was annoying at the time that his name was mentioned along with Winston Churchill's son-in-law, the late Duncan Sandys, the Colonial Secretary, as the man in the photographs. 'I thought the best thing to do was to say nothing and it would die out.'
The Argyll divorce proceedings were sensational by any standards. The Duke and his daughter burgled the Duchess's London residence searching for her diaries and compromising pictures.
He charged that she had committed adultery with three named men and an unknown fourth person - the headless man.
The judge, Lord Wheatley, revealed the most intimate details of their lives in a 50,000-word judgment of unprecedented severity that condemned the Duchess as wholly immoral.
The proceedings began in 1959 and ended in May 1963, one month before Harold Macmillan asked Lord Denning to investigate the Profumo affair. The photographs from the Argyll divorce were relevant because of allegations that the headless man was a government minister.
Lord Denning found this was not so. Duncan Sandys underwent a medical examination which showed in 'unmistakable and significant respects' that his physical characteristics were different from the 'unknown' man. Furthermore, his handwriting did not match that on the photographs and paper in which they were wrapped. In his report Lord Denning said: 'There was further evidence before me (which was not before the judge in the Argyll divorce case) which indicated who the 'unknown man' was. But I need not go into it here . . . '
Last week Lord Denning shed more light. The 'further evidence' he had referred to was handwriting, he said. A second man had come to see him about the photographs and, before he was admitted to his office, Lord Denning asked the doorman to get the man to sign his name in capital letters on an entry form. He made this request because writing on the photographs was in capitals.
'The writing was exactly the same so I was able to say who it was as I had the handwriting on the entry form and on the photographs,' Lord Denning said.
And was it Mr Fairbanks? 'If you guess that you may guess right. But I won't disclose who it was as I promised that the information I gathered would be entirely confidential.' Mr Fairbanks did come to see you? 'Yes.'
'Lord Wheatley was right in his judgment,' Lord Denning said. 'The Duke and Duchess were very prominent and if they fell short they could expect to be criticised.'
Barbara Cartland, 92, one of her few friends alive today, said Margaret Argyll was promiscuous. 'She was very beautiful and every man wanted to go to bed with her and she wanted to go to bed with every man. And why not? There's nothing wrong with that. She did go from man to man. She didn't have love affairs which lasted a long time. I think men found her rather boring after a time.'