This flawless, 108-carat stone is legendary. It was first written about in 1304, when it belonged to an Indian potentate, the Rajah of Mulwar. It remained in his family for 200 years until it fell into the hands of a rival mogul emperor, the Sultan of Babur.
Meanwhile, the Shah of Persia had heard rumours of a fabulous diamond, and became so obsessed that he ransacked Delhi in his search for it. In 1739, the Shah held the Sultan of Babur captive, but the elusive diamond was still nowhere to be found. The Shah was at his wits' end when a member of the Sultan's harem tipped him off that the great diamond was hidden inside her employer's turban.
Armed with this inside information, the Shah invited the emperor to dinner and took advantage of an old custom involving the exchange of turbans. No sooner had he got the Sultan's than the Shah shot off to unroll it and out tumbled the gem. It is said that on seeing it he exclaimed "Koh-i-noor!" ("Mountain of light!"), which is what it has been known as ever since.
Sadly, the Shah did not enjoy his prized possession for long, as he was assassinated soon afterwards. The diamond ended up in a jewel chamber in Lahore, from where it was appropriated by the British in 1849 "as partial indemnity for the Sikh wars". It was presented to Queen Victoria after the annexation of the Punjab by the British East India Company.
Queen Victoria preferred trinkets with sentimental value - lockets containing her children's hair, or bracelets with portraits on them - to whopping sparklers, but she still understood the regal symbolism of a great stone and treated the Koh-i-noor with the respect it deserved. When the public complained that it wasn't glittery enough when it went on display at the Crystal Palace exhibition, she sent it to Amsterdam to be recut. When it returned its fire was enhanced but at the expense of its caratage. The stone was eventually set in a diadem for use at state occasions.
After Albert's death, Victoria didn't have much call for jewels, but on her first public appearance, four years' after being widowed, she wore the Koh-i-noor as a brooch.
The diamond was left to her daughter-in-law, Alex-andra, who was thought to have worn it in her coronation crown. But strangely, it has been discovered that all the jewels in that coronation crown are fake, including the great central diamond. The theory is that she was crowned in paste because the real thing was intolerably heavy.
However, every queen consort since then has worn the Koh-i-noor in a coronation crown, and the Queen Mother now uses it in one of her tiaras.
Perhaps because of the blood that was shed in its cause, legend has it that the diamond brings bad luck to any man that wears it. The next likely wearer will be Prince William's consort.
The Indian government has been trying to reclaim the diamond since 1953. But the British, as usual, are obdurate in their refusal to hand it back, saying that the Koh-i-noor's history is so complicated that no one country can claim ownership. When it's not in use, you can see it on display with the Crown Jewels.