Fine Sapphire and Diamond Ring, Harry Winston. Photo Sotheby's

Centring on a cushion-shaped sapphire weighing 7.68 carats, to a stylised mount set with baguette and brilliant-cut diamonds together weighing approximately 1.10 carats, mounted in platinum, signed. Ring size: 5½. Estimation: 5,500,000 - 6,500,000 HKD

Accompanied by Gübelin and SSEF reports numbered 13011034 and 67030, stating that the 7.68 carat sapphire is natural, of Kashmir origin, with no indication of heating.

Sotheby's Hong Kong. Magnificent Jewels and Jadeite. 8 April 2013 www.sothebys.com