The most valuable cut diamond ever to be offered at auction has gone on display in London.

The Pink Star is expected to sell for more than €55 million.

The auction record is currently held by the Oppenheimer Blue, which fetched €40 million at Christie's in Geneva, Switzerland, last year.

At 59.60 carats, the Pink Star is more than twice the size of the Graff Pink - the 24.78-carat gem which holds the pink diamond auction record.

The Pink Star sold for almost €60 million at an auction in Switzerland in 2013, but is back on the market after the sale defaulted.

David Bennett, Sotheby's jewellery division's worldwide chairman, said: "At a time of unprecedented demand for the finest in coloured diamonds, I am delighted to be bringing this magnificent stone back to the market."

The extraordinary size of this 59.60-carat diamond, paired with its richness of colour, surpasses any known pink diamond recorded in history

"The extraordinary size of this 59.60-carat diamond, paired with its richness of colour, surpasses any known pink diamond recorded in history."

The diamond is on display at Sotheby's London offices before its sale on April 4 in Hong Kong.

Mined by De Beers in Africa in 1999, the 132.5-carat rough diamond was cut and polished over a period of two years.