The Koh-i-Noor (Persian for 'Mountain of Light'; /ˌkoʊɪˈnʊər/ KOH-in-OOR),[b][4][5] also spelt Koh-e-Noor, Kohinoor and Koh-i-Nur, is one of the largest cut diamonds in the world, weighing 105.6 carats (21.12 g).

The young king ruled under the shadow of the Company ally Gulab Singh, the first Maharaja of Jammu and Kashmir, who had previously possessed the stone.

By modern standards, the culet (point at the bottom of a gemstone) is unusually broad, giving the impression of a black hole when the stone is viewed head-on; it is nevertheless regarded by gemologists as "full of life".

[24] However according to recent research, the story of Borgia cutting the diamond is not correct, and most probably mixed up with that of the Orlov, part of Catherine the Great's imperial Russian scepter in the Kremlin.

When looking at the Mughal treasury, Abu'l-Fazl ibn Mubarak, the Grand vizier to Akbar, noted that red spinels and Burmese rubies had become the most desirable jewels by the nobility.

[11] During this time the Persian new year ceremony, Nowruz, had become a period in which the subjects could bring offerings of gems and money to the imperial family in exchange for political promotions within the greater bureaucracy.

Following the overthrow of the Safavid dynasty of Persia two years earlier, he began raiding Mughal territory before soon launching a full-scale invasion of North-West India.

This invading force soon captured Delhi where, after a massacre of the civilian population, the army began a systematic looting of the wealth of the city and the treasury of the Mughal Empire.

[27] Nader Shah's biographer, Muhammad Kazim Marvi, first recorded seeing the Koh-i-Noor in the 1740s on the head of one of the peacocks on the throne, along with other prominent gems such as the great Timur Ruby and the Daria-i-Noor.

[31] He was quickly overthrown, but fled with the diamond to Lahore (in modern Pakistan), where in one account, Ranjit Singh, founder of the Sikh Empire, in return for his hospitality, insisted upon the gem being given to him, and he took possession of it in 1813.

[48] The presentation of the Koh-i-Noor by the East India Company to the queen was the latest in a long history of transfers of the diamond as a coveted spoil of war.

[49] Duleep Singh had been placed in the guardianship of Dr John Spencer Login, a surgeon in the East India Company Army serving in the Presidency of Bengal.

[50] In due course, the Governor-General received the Koh-i-Noor from Dr Login, who had been appointed Governor of the Citadel, on 6 April 1848 under a receipt dated 7 December 1849, in the presence of members of the Board of Administration for the affairs of the Punjab: Sir Henry Lawrence (President), C. G. Mansel, John Lawrence and Sir Henry Elliot (Secretary to the Government of India).

It was then sent to England for presentation to Queen Victoria in the care of Captain J. Ramsay and Brevet Lt. Col F. Mackeson under tight security arrangements, one of which was the placement of the dispatch box in a larger iron safe.

On arrival in Britain on 29 June, the passengers and mail were unloaded in Plymouth, but the Koh-i-Noor stayed on board until the ship reached Spithead, near Portsmouth, on 1 July.

[55] At first, the stone was put inside a gilded birdcage, but after complaints about its dull appearance, the Koh-i-Noor was moved to a case with black velvet and gas lamps in the hope that it would sparkle better.

[58] After consulting mineralogists, including Sir David Brewster, Victoria's husband Prince Albert with the consent of the government decided to have the diamond re-cut.

[26] On 17 July 1852, the cutting began at the factory of Garrard & Co. in Haymarket, using a steam-powered mill built specially for the job by Maudslay, Sons and Field.

[26] Although Prince Albert was dissatisfied with such a huge reduction, most experts agreed that Voorzanger had made the right decision and did the job with impeccable skill.

[60] When Queen Victoria showed the re-cut diamond to the young Maharaja Duleep Singh, the Koh-i-Noor's last non-British owner, he was apparently unable to speak for several minutes afterwards.

In a letter to her eldest daughter, Victoria, Princess Royal, she wrote in the 1870s: "No one feels more strongly than I do about India or how much I opposed our taking those countries and I think no more will be taken, for it is very wrong and no advantage to us.

[71] They were kept in leather hat boxes under lock and key in the office of the Royal Librarian Sir Owen Morshead until 1941 when they were transferred to a specially dug tunnel under the walls of the castle.

At this time Morshead and the Keeper of the Tower Armouries removed some of the larger stones, including the Koh-i-Noor, and wrapping them in cotton wool, inserted them in a glass preserving-jar, which was then placed in a biscuit tin; the thinking being that, unlike the bulkier crowns, this would allow their swift relocation if the German invasion occurred.

[74] British officials said that a variety of claims meant it was impossible to establish the diamond's original owner,[75] and that it had been part of Britain's heritage for more than 150 years.

[76] In July 2010, while visiting India, David Cameron, the Prime Minister of the United Kingdom, said of returning the diamond, "If you say yes to one you suddenly find the British Museum would be empty.

"[79] In 1976, Pakistan asserted its ownership of the diamond, saying its return would be "a convincing demonstration of the spirit that moved Britain voluntarily to shed its imperial encumbrances and lead the process of decolonisation".

[58] The Koh-i-Noor was one of the inspirations for the eponymous gemstone in The Moonstone (1868), a 19th-century British epistolary novel by Wilkie Collins, generally considered to be the first full length detective novel in the English language.

In his preface to the first edition of the book, Collins says that he based his eponymous "Moonstone" on the histories of two stones: the Orlov, a 189.62-carat (37.9 g) diamond in the Russian Imperial Sceptre, and the Koh-i-Noor.

[85] The Koh-i-Noor also features in Agatha Christie's 1925 detective novel The Secret of Chimneys where it is hidden somewhere inside a large country house and is discovered at the end of the novel.

[86] The Koh-i-Noor is a central plot point in George MacDonald Fraser's 1990 historical novel and satire, Flashman and the Mountain of Light, which refers to the diamond in its title.