An Escada-cut diamond single-stone ring. photo courtesy Bonhams

The Escada-cut diamond, weighing 10.01 carats, between rectangular fancy-cut diamond shoulders, ring size N½ - Estimate: £35,000 - 40,000. Unsold

Accompanied by an International Gemological Institute (IGI) certificate stating that the diamond is Fancy Yellow, natural colour, SI1 clarity. Certificate number 2-286-9636, dated 28 May 2010.

Note: The Escada cut, created exclusively for the eponymous luxury fashion house, is a 12 sided cut with 97 facets, designed to maximise fire through the crown and table facets and to emit a star pattern through the culet. The cut is meant to symbolise the 12 months of the year and their ever-renewing cycle.

Bonhams. Fine Jewellery, 22 Sep 2010 New Bond Street www.bonhams.com