In March 1963, he went before the House of Commons to try to quell rumors about a sexual relationship. “There was no impropriety in my acquaintanceship with Miss Keeler,” he said.
But details kept coming out — British newspapers called it the “Scandal of the Century” — and he resigned in June 1963.
“I said that there had been no impropriety,” Mr. Profumo said in his letter of resignation. “To my very deep regret I have to admit that this was not true.”
Ms. Keeler had had multiple lovers, among them Cmdr. Eugene Ivanov, an attaché in the Soviet Embassy in London, and when that relationship came to light, government figures and MI5, the domestic intelligence agency, feared that her affair with Mr. Profumo might have created a grave security breach.
When Mr. Macmillan resigned later in 1963, the Profumo affair was often cited as a contributing factor.
Mr. Profumo died in 2006, having rarely spoken about the matter again. His wife, the movie actress Valerie Hobson, stood by him throughout, until her death in 1998 at 81.
Ms. Keeler, though, had a lot to say about the scandal over the years, including in “Secrets and Lies,” a memoir written with Douglas Thompson and published in 2012.
“I enjoyed sex and I indulged in it when I fancied the men,” she wrote, “but I was no hypocrite. It was others who were disguising their peccadilloes in dinner jackets, diamonds and evening dresses, indulging in weird fantasies.”
Christine Keeler was born on Feb. 22, 1942, outside London in Uxbridge. She left home at 16 and was dancing in a topless club in London when she met Stephen Ward, an osteopath who moved in fashionable circles.
“In reality,” she wrote in the book, “Stephen Ward was a spymaster who befriended hosts of prominent and powerful people in the British government, aristocracy and even members of the royal family.”
Newspapers said Mr. Ward ran a “vice ring.” He committed suicide in August 1963.
He introduced Ms. Keeler to Mr. Profumo in July 1961, at Cliveden House in Buckinghamshire. She had been swimming nude, “with Profumo watching approvingly,” Ms. Keeler’s book said.
Mr. Profumo, she wrote, seemed not to be a first-timer when it came to illicit affairs. (Headlines just last week in…