The world's biggest diamond

The world's biggest diamond, believed to be twice the size of the Cullinan, has been discovered in the North-West Province of South Africa. The find has electrified the diamond community, but the circumstances of the discovery are shrouded in mystery.

The diamond is expected to attract furious bidding from buyers worldwide and could fetch up to £15m.The 203 carat Millennium Star is the second biggest flawless diamond. The newly found stone could produce a stone even bigger.

A spokesman for the mining house which made yesterday's find, Brett Joli, said the diamond was being rushed to a bank vault in Johannesburg and would be kept there for a couple of days "until we calm down and decide what we are going to do". A security company was being hired to protect the precious stone.

The mining company which made the find has not been identified.

The South Africa Broadcasting Corporation said the stone was said to be twice the size of the Cullinan diamond.

Fred Cuellar, the founder of Diamond Cutters International and author of How to Buy a Diamond, said he first heard about the find a few days ago. "I get a phone call when any rare stone around the world is found and when I heard about this one it was stunning news.

"It caught everybody in the diamond industry offside. There will be a lot of mad bidding from a lot of private individuals as to who is going to buy this stone."

The Cullinan, which was found near Pretoria more than a century ago, was until recently acknowledged to be the largest cut diamond in the world, weighing in at 530.20 carats. In 1985 it lost the record to the Golden Jubilee, which was found in the same mine as the Cullinan and weighed 545.67 carats.

In its rough state the Cullinan weighed 3,106.75 carats. It now forms part of King Edward's sceptre and is in the Tower of London.

The Cartier diamond, famous as a gift from Richard Burton to Elizabeth Taylor, weighed a mere 240.80 carats rough and 69.42 carats cut.