The Koh-I-Noor which means "Mountain of Light" in Persian, it is a 105 carat diamond (in its most recent cut) and was once the largest known diamond in the world.

The diamond was mined in the Kollur mines near the village Kollur. The diamond became the property of Kakatiya kings who installed it as a Goddess's eye in a temple in the capital city of Wa Koh-I-Noor rangal. Then the diamond passed through the hands of the rulers of the Delhi sultanate before finally passing to Babur, who is the first Mughal emperor, in 1526.

The first confirmed historical mention of the Koh-I-Noor was in 1526. The Mughal Emperor Shah Jahan, famous for building the Taj Mahal, had the stone placed into his ornate Peacock Throne. It stayed in the throne until the invasion of Nader Shah in 1739 with the sacking of Agra and Delhi. The Peacock Throne was carried away along with the Koh-I-Noor to Persia in 1739. Nader Shah was then assassinated in 1747 and the stone came into the hands of Ahmed Shah Abdali of Afghanistan. In 1830, Shah Shuja the ruler of Afghanistan managed to flee with the Koh-I-Noor diamond. He then came to Lahore where he gave it to the Sikh Maharaja (King) of Punjab.

Maharaja Ranjit Singh was then crowned ruler of Punjab and willed the Koh-I-Noor to the Jagannath Temple in Orissa from his deathbed in 1839. After his death the British administrators did not execute his will. On the 29th March 1849, the British raised their flag on the citadel of Lahore and the Punjab was formally proclaimed to be part of the British Empire in India. One of the terms of the Treaty of Lahore, the legal agreement formalizing this occupation, was as follows:

The gem called the Koh-I-Noor which was taken from Shah Shuja-ul-Mulk by Maharajah Ranjit Singh shall be surrendered by the Maharajah of Lahore to the Queen of England.

When the boat that was carrying the Koh-I-Noor arrived in Britain the passengers and mail were unloaded from the boat in Plymouth. However the Koh-I-Noor remained on board until the ship reached Portsmouth, from where Lawrence and Mansel took the diamond to the East India House in the City of London and passed it into the care of the Chairman and Deputy Chairman of the East India Company.

The handing over of the Koh-I-Noor diamond to The Queen on 3 July 1850 as part of the terms of the conclusion of the Sikh War also coincided with the 250th anniversary of the East India Company. After Queen Victoria's death it was set in Queen Alexandra's brand-new diamond crown, with which she was crowned at the coronation of her husband, King Edward VII. Queen Alexandra was the first Queen Consort to use the diamond in her crown, followed by Queen Mary and then Queen Elizabeth.

The diamond is now set into the crown worn by the female consort to Monarch of the United Kingdom, and is still currently in the Crown of Queen Elizabeth (the late Queen Mother).