The Koh-i-Noor diamond was mined at a location near Masulipatnam, according to an account by Theophilus Metcalfe made at the request of Lord Dalhousie. It was owned by many illustrious Kings, including the Iranian Nadir Shah  and those of the Ghori  Dynasty, Timurid Dynasty and the Afghan Durranis, before Ranjit Singh acquired it from Shuja-ul-Mulk.

The Maharaja was curious about the gem's value. When Wafa Begum, the beloved wife of the Koh-i-Noor's last owner, was asked, she replied, "If a strong man were to throw 5 stones, 4 in cardinal directions and 1 vertically upwards, and the space in between was filled with gold and precious stones, it still wouldn't equal the value of the stone."

Ranjit Singh died in 1839. The empire had just begun recovering from the great loss when circumstances forced it into two prolonged wars. Following the defeat of Punjab in the Second Anglo-Sikh War, the Last Treaty of Lahore was signed. In Article 3 of the treaty, the British demanded that the Koh-i-Noor be surrendered to the Queen of England. The conditions under which this treaty was signed were, however, those of deep duress. Not only was an additional regiment stationed outside Lahore, but the Resident of Lahore was also given instructions to impose British rule regardless of the outcome of the deliberations of the Council of Regency.

Its retrieval, however, encountered unforeseen problems. While removing the box from the chest, Mr Muspratt, the Treasurer, pulled on the lid handle, causing the red tape to split, the seal to break, and the box to open. The only men to know of the inner contents of the despatch box were Dalhousie, Mackeson and Ramsay. Given the absence of the Governor-General, the two military men asked the Treasurer to vacate the room so they could examine the Koh-i-Noor at close range. Once satisfied, they collected their package and headed to the ship.

The HMS Medea under Captain Lockyer was chosen as the vessel to carry the Diamond across the seas. It carried the invaluable gem to Plymouth, where Mr Onslow, the Secretary to the Chairman of the East India Company, greeted Mackeson and Ramsay. Mr Onslow was to accompany the two men to London at the earliest. It is at this stage that some discrepancies begin to emerge. There are two letters from Mackeson and Ramsay to Melville and Dalhousie, respectively, recounting two differing narratives of their trip to London. The lack of clarity about the multiple custodians of the Diamond before its arrival in England sparked suspicions among the Court of Directors about the authenticity of the Royal gift. These, however, were overcome when both the Governor General of India and the Secretary to the Governor General supported the testimonies of the two officers.

Having arrived in England on 29 June 1850, the 3 men reached the India Office in London on 2 July 1850. The Diamond was gifted to the Queen on 3 July 1850, the 250th Anniversary of the EIC.

In 2016, the Government of India took the stand that the Diamond was not a gift and had been forcibly taken from Maharaja Duleep Singh. They stated that, given historical evidence, the Indian credentials of ownership of the Koh-i-Noor could not be doubted. Of late, we have seen some European countries agree to repatriate artefacts at the request of their former Colonies. An example from December 2018 is the French President's promise to return 26 artworks taken from Benin, and a British museum's recent decision (February 2019) to return the hair, cut from the head of Emperor Tewodros II, to Ethiopia.