A collection of letters sent by Rolling Stones frontman Mick Jagger to his secret lover in the summer of 1969 sold for around £185,551 (RM916,950.28) at a London auction on Wednesday, trumping their pre-sale estimate.

Purchased by a private collector over the telephone, the letters sold for £187,250 (RM 753,313.33) at a Sotheby's auction, trumping their pre-sale estimate of £70,000( RM281,612.46) to £100,000
(RM402,303.51)

The letters were written to black American singer Marsha Hunt, aged 23 at the time, while Jagger was filming the movie "Ned Kelly" in Australia, and were presented as a window into a different side of the rock-and-roll legend.

"We are delighted with the result of todays sale which reflects the great significance of these letters, written at such a vivid moment in social and musical history," said Sotheby's books specialist Gabriel Heaton.

"There has been enormous international interest in the letters, which depict Mick Jagger, not as the global superstar he is today, but reveal him as a poetic and self-aware 25-year-old with wide-ranging intellectual and artistic interests."

Hunt, who starred in the original London cast of hit musical "Hair" and was the poster girl of the "Black is Beautiful" movement, had an initially clandestine affair with the rocker when interracial relationships were taboo.

"1969 saw the ebbing of a crucial, revolutionary era, highly influenced by such artists as The Beatles, The Rolling Stones, James Brown and Bob Dylan," Hunt said after the sale.

"Their inner thoughts should not be the property of only their families, but the public at large, to reveal who these influential artists were -- not as commercial images, but their private selves."

Written after the Stones' historic Hyde Park gig, the letters illustrate Jagger's musings on topics like the moon landing, his future relationship with Hunt, his impressions of the Outback and John Lennon and Yoko Ono.

Hunt said: "Despite his high profile and my own... our delicate love affair remains as much part of his secret history as his concerns over the death of Brian Jones and the suicide attempt of his girlfriend, Marianne Faithfull."

Hunt is the inspiration behind the Stones' 1971 hit "Brown Sugar" and became the mother of Jagger's first child, Karis.