Miners unearth world's biggest diamond

· South African find is twice as big as the Cullinan
· Expert predicts feverish bidding on huge stone

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.

Rock stars

· The Cullinan Diamond was discovered in 1905 and at 3,106 carats was the largest gem-quality rough diamond ever found. Cullinan I, or the Great Star of Africa - at 530 carats formerly the largest cut diamond - was one of the 105 gems cut from it.

· The Koh-i-noor is part of the British crown jewels. It originated in India but seized by Britain as a spoil of war in 1849. The diamond supposedly brings good luck to female owners and misfortune or death to any male who wears or owns it.

· The Hope Diamond is a large (45.52 carat), deep blue diamond. It is legendary for the curse it supposedly puts on whoever possesses it. Previous owners include Kings Louis XV and XVI and Marie Antoinette.