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The library of London School of Economics philosopher Sir Karl Popper, which is to be sold by Sotheby's, is expected to fetch Pounds 500,000.

Austrian-born Sir Karl, who died last year aged 92, boasted a working library of 6,000 volumes, collected mainly after his post-war arrival in England. It will be kept intact and sold as a single lot, probably raising Pounds 200,000.

The books, which filled almost every room of his Surrey house and meant that the only available flat surface for him to work on was the top of his grand piano, reflect the genesis of his key ideas.

Many of them carry his signature and handwritten annotations. In the copy of Bertrand Rusell's Human Knowledge, Popper has written: "Russell said to me: 'If I had heard before what you said today, I would not have written Human Knowledge'."

Also under the hammer are his collection of master copies of his own works including The Open Society and its Enemies, which is expected to fetch Pounds 50,000; a letter from Albert Einstein that gave Popper a resume of the celebrated imaginary experiment showing that quantum mechanics could not give a complete description of physical reality; and more than 300 antiquarian books dating back to 1480.