The defeated Sikhs were forced to give up the gem

and took it to Afghanistan. One of his descendants then fled with it to Lahore, where Ranjit Singh took possession of it in 1813. It had been in the hands of the Sikhs for just 36 years before Duleep Singh was forced to hand it over to the British.

In December 1849, it was handed over to the Governor-General of India and in February 1850 was sealed inside an iron safe and a red dispatch box to be sent to England by ship. The vessel encountered stormy weather and there were fears that it might have foundered.

The diamond duly arrived in England, though, where it was first handed to the chairman of the East India Company. On July 3, 1850, it was presented to Queen Victoria in person by the young Duleep Singh, who had been brought over from Lahore specially to do so.

The following year it was displayed i nside a red tent at the Great Exhibition in Hyde Park, where tens of thousands gawped at it through iron bars. Gaslight flickered around it, making it sparkle.

What was most noticeable, besides its enormous size, was its comparative ugliness. It had never been the prettiest of diamonds, which is why Prince Albert then had it re-polished and re-shaped at Garrards, the crown jewellers. The Dutch expert who carried out the work discovered several flaws, which he cut away.

This made it a perfect and more pleasing oval but reduced its size by more than a third, from 186 carats (37.2 grams/ 1.3oz) to 105.6 carats ( 21.1 grams/ 0.75oz). It was then mounted in a tiara for Queen Victoria and later reset, first into Queen Mary’s Crown and finally into the Queen Mother’s crown f or the coronation of George VI in 1937.

That crown is now with the rest of the Crown Jewels in the Tower of London. Whether this will be its last resting place remains to be seen. British governments have, however, consistently resisted outside claims of ownership.

On a visit to India in 2013, David Cameron made i t clear that he wouldn’t relinquish the Koh-i-Noor.

‘I don’t believe in “returnism”,’ he declared. In other words, the only way the jewel might be taken back is if another vast Sikh army lays siege to the Tower.