A diamond single-stone ring. photo Bonhams

The marquise-cut diamond, weighing 13.41 carats, within a six-claw setting, between épaulette-shaped diamond shoulders, remaining diamonds approximately 1.25 carat total, ring size J. Estimate: £250,000 - 300,000, US$ 400,000 - 480,000

Accompanied by a certificate from GIA stating that the diamond is H colour, VS1 clarity. Certificate number 13785963, dated 2nd April 2009.

Bonhams.Fine Jewellery, 25 Apr 2012. London, New Bond Street www.bonhams.com