8 February 2011 Last updated at 19:43 ET

Picasso painting La Lecture fetches £25m at auction

Picasso kept his relationship with Marie-Therese Walter secret for many years

A portrait of the muse who transformed painter Pablo Picasso's life has sold for £25.2m ($40.7m) at Sotheby's auction house in London.

La Lecture went to an anonymous phone buyer after six minutes of bidding.

The masterpiece depicts Picasso's secret lover, Marie-Therese Walter, who was 17 when Picasso, then 45, met her in Paris for the first time.

Their relationship was kept secret for many years because of her age and because Picasso was married.

Ms Walter later said she had never heard of the artist when he first approached her saying: "I am Picasso - you and I are going to do great things together."

Until La Lecture was painted, Ms Walter had only appeared in Picasso's works in code with her features often embedded in the background of his paintings.

It was when the picture was exhibited at a Picasso retrospective that the artist's wife, Olga Khokhlova, realised there was another woman in his life and their marriage subsequently broke up.

Ms Walter later had a daughter, Maya, with Picasso.

Ms Walter inspired a number of works including La Reve as well as Nude, Green Leaves and Bust, both painted in 1932.