LONDON — In November 1967, four years after her husband’s assassination, Jacqueline Kennedy traveled to the temples of Angkor Wat in Cambodia on a much-publicized trip with David Ormsby Gore, a friend of her husband and himself a recent widower.

There was much speculation of a romantic attachment. A few months later, Mr. Ormsby Gore, a former British ambassador to Washington, proposed marriage. She turned him down.

In a handwritten letter, filled with anguish and a touch of cruelty, she explained her decision to marry Aristotle Onassis instead.

“If ever I can find some healing and some comfort — it has to be with somebody who is not part of all my world of past and pain,” she wrote. “I can find that now — if the world will let us.”