A diamond necklace that has not seen the light of day for over 40 years has become the most expensive diamond necklace to be sold at auction outside of London.

The necklace was consigned to Duke’s Auctioneers of Dorset from a distinguished private collection. It remained in a safe until recently when it was worn during the auction viewing for the first time since the 1960s. It sold for a total of £231,800.

The diamond necklace, dating to the 1860s, is set with 53 cushion-cut diamonds which total in excess of 64cts.

Amy Brenan, jewellery valuer at Duke’s in Dorchester, said: “The largest diamond is 5cts, approximately the same size as a ladies ring finger nail, with the rest of the diamonds graduating along the neckline.

“These necklaces were known as ‘rivieres’ – the idea of a literal ‘river’ of diamonds gracing the wearer’s neck was incredibly seducing to the Victorians.

“ Rivieres were common at this time but to find such a large one in original condition with an additional pendant drop is extremely exciting.”

The quality of the piece and the exceptional colour and clarity of the diamonds attracted interest from diamond buyers and private collectors across the world.

“Each mount for each diamond is engraved with the old weight of the diamond in grains instead of carats’ said Amy.

“This is how diamonds were measured in the 19th century and it illustrates how important the Goldsmith thought the stones were.

It is highly unusual to see this engraving and I think this gave buyers the confidence to bid strongly. It was not a piece to be missed.”

The diamond riviere necklace was fought over by three telephone bidders and a lady in the room, with the hammer falling at £190,000 (£231,800 inc. buyers premium) to an anonymous bidder.

It breaks the current house record for a piece of jewellery at Duke’s by more than £100,000: In 2010, the auction house sold an emerald turban brooch designed by Paul Iribe for over £84,000.

Duke’s next Jewellery and Silver sale will be held on 13th June 13