A diamond single-stone ring. photo Bonhams

The step-cut diamond, weighing 4.23 carats, to tapered baguette-cut diamond shoulders, ring size J½. Estimate: £70,000 - 90,000, US$ 110,000 - 140,000

Accompanied by a certificate from AnchorCert stating that the diamond weighing 4.23 carats is D colour, VVS1 clarity. Certificate number 20001915, dated 6th March 2012.

Accompanied by a certificate from Ricerch e analisi gemmologiche stating that the diamond weighing 4.23 carats is D colour, VVS1 clarity. Certificate number D008/11, dated 01/04/2011.

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