A rare flawless blue diamond that was once part of the De Beers Millennium collection is expected to fetch almost £4 million at auction.
It is being put up for sale by a private collector and is the star lot at Sotheby's Hong Kong jewels and jadeite 2010 spring sale on April 7 and bidding is expected to reach the £3.8 million ($5.8 million) estimate price.
