Auction house Christie's is planning to stage what it believes will be London's biggest art sale.

Up to 120 pictures will be sold, which the company believes could be worth at least �50m.

At the centre of next Monday's sale will be Pablo Picasso's Femme dans un fauteuil (Woman In An Armchair), which is valued at up to �6m.

The Picasso market has become very firm - there is interest from all over the world Jussi Pylikkannen Christie's

"It will be the biggest sale night London has ever had," Christie's impressionist art director Jussi Pylikkannen.

The Picasso work features the Spanish master's lover Marie-Therese Walters , and is a sister work of his Nu au collier (Nude With Necklace), which became the most expensive impressionist painting in the world last year when it sold for �15.9m.

It is one of seven pictures in the sale by Picasso.

"He is the genius of the 20th Century, the Mozart of the picture world," Mr Pylkkanen said.

'Iconic'

"The Picasso market has become very firm. There is interest from all over the world," he added.

Works by Cezanne, Degas, Duffy, van Gogh and Monet also feature in the sale, which will be divided into impressionist and modern, German and surreal sections.

Heading the surrealist section will be Rene Magritte's Les Barricades Mysterieuses, priced at up to �2.2m.

"This is a truly iconic image from Magritte. It is from his empire of lights series that he painted between 1948 and 1962," surrealist expert Oliver Camu said.

"There is a lot of interest in surreal art, but it still has a long way to go compared with the more established impressionist and modern art market," he added.

Works by Dali, Miro and Ernst will also feature in the sale.