UK- Princess Diana had a passionate one-night stand with John F Kennedy Jr, it was claimed tonight.

The pair had a steamy fling, which Diana described as “pure chemistry,” according to a new book by friend and confidante Simone Simmons.

She rated Kennedy “ten out of ten” in bed, and said their session in a New York hotel was “pure lust,” Simmons claims.

The author, whose book ‘Diana: the Last Word’ is serialised in the Sun, said the princess fantasised about becoming America’s First Lady.

She said she had kept the saucy secret for a decade but now wanted the world to know Diana had found happiness after Prince Charles.

Kennedy died in a plane crash two years after Diana was killed in Paris in 1997.