LONDON (REUTERS).- Portraits of three different lovers of 20th century master Pablo Picasso fetched the three highest prices at a London auction at Christie’s on Tuesday, the first in a key series of art sales over the coming weeks. Top lot on the night at the impressionist and modern art evening sale was a depiction of Dora Maar, who became Picasso’s lover and muse at the expense of Marie-Therese Walter. The 1939 work, which had been unseen in public since 1967, sold for 18.0 million pounds ($29.1 million), several times the pre-sale estimate of 4.0-8.0 million pounds. The second highest price paid on the night was for “Jeune fille endormie,” a 1935 portrait of Walter that went under the hammer for 13.5 million pounds ($21.9 million). The painting, valued at 9.0-12.0 million pounds, was given to the University of Sydney in 2010 by an anonymous donor on the condition that it was sold and that the proceeds went to the univers