Sir Mick Jagger's love letters are being put up for auction.

The Rolling Stones rocker penned a series of 10 letters in 1969 to his former flame, American singer Marsha Hunt - who inspired the band's hit 'Brown Sugar' and bore his first child - which will be auctioned off at Sotheby's in London this December.

Marsha said in a statement: ''When a serious historian finally examines how and why Britain's boy bands affected international culture and politics, this well-preserved collection of Mick Jagger's hand written letters will be a revelation.''

Marsha, 66, has revealed the correspondence chronicles their ''delicate love affair'' and says the letters were written from the set of Mick's film 'Ned Kelly' in Australia.

They discus topical subjects of the moment like the first moon landing and John Lennon and Yoko Ono's relationship.

Sotheby's books specialist Gabriel Heaton said the collection - which includes song lyrics and a Rolling Stones playlist - shows a ''poetic and self-aware'' young Mick.

He added: ''They provide a rare glimpse of Jagger that is very different from his public persona: passionate but self-contained, lyrical but with a strong sense of irony.''

The auction will take place on December 12 and is expected to fetch between £70,000 and £100,000.