In the summer of 1969, Mick Jagger, the sizzling frontman of Rolling Stones, fell in love with a beautiful black American singer Marsha Hunt, who was the inspiration for 1971 track, Brown Sugar from the album Sticky Fingers.
A set of 10 love letters Jagger wrote to Hunt while shooting the movie Ned Kelly in Australia to tide over a period of crisis was sold for 187,250 pounds by Sotheby's in London on Wednesday.
The relationship with Hunt was Jagger's closely guarded secret.
Jagger was at that time at the height of his creative powers and Hunt was the image of "Black is Beautiful" and the landmark West End production of Hair.
A spokesperson for Sotheby's said the letters were "beguilingly beautiful with a wide range of cultural interest".
They shed new light on the musician, who has survived through decades of highs and lows of musical career.
The letters included lyrics of Rolling Stones tracks and a playlist.
The letters written from Tony Richardson's film sets in the Australian outbacks touch upon subjects that played on Jagger's mind - as distant as the moon landing, John Lennon and Yoko Ono's affairs, Christopher Isherwood and Isle of Wight festival.
"The letters were addressed to me," says Hunt.
"I was 23, America-born, Berkeley-educated and London-based. Despite his high profile and my own as a singer, actress, a Vogue model and a star of London's original cast of Hair, our delicate love affair remains as much a part of his secret history as his concerns over the death of Brian Jones and the suicide attempt by his girlfriend Marianne Faithfull," Hunt says.
Gabriel Heaton, Sotheby's books specialist, said the "beautifully written and lyrical letters from the heart of the cultural and social revolution of 1969 frame a vivid moment in the cultural history".
"Here we see Mick Jagger not as a global superstar he had become but as a poetic and self-aware 25-year-old with wide-ranging artistic and intellectual interests," he said.
The letters, written after the Rolling Stones Hyde Park concert, reveal Jagger as a "passionate but self-contained, lyrical but with a strong sense of irony".
Hunt recounts that in the summer of 1969, she was approached by the Rolling Stones office to shoot for the track Honky Tonk woman in a skimpy dress. Hunt refused. After failing to get her in on telephone, Jagger appeared at the doorstep of her Bloomsbury apartment one midnight.
As she recalled in her 1986 memoir Real Life, Jagger stood, "framed by the doorway grinning with a dark coat".
"He drew one hand out of his pocket and pointed it at me like a pistol...Bang".
It was the start of a passionate and initially clandestine affair, Hunt writes in her memoirs.
The experience on the set in Australia was not a pleasant one for
Jagger. Jagger's hand was badly burnt when a prop pistol misfired and he was ultimately disillusioned with movies.