That legacy is now being claimed by Amsterdam resident Beant Singh Sandhanwalia, officially recognised by the Punjab government as the heir to Duleep Singh.

A report in The Sunday Times today says that the key to the diamond's ownership is contained in the safe-deposit box, belonging to Duleep Singh's daughter Catherine.

Contents of the box, which was deposited with a Swiss bank before Catherine died in 1942, are known only to a small group of bankers, but are thought to include papers that will settle the issue of who the true successor to Duleep Singh and, thereby, the diamond's owner, is. The box could also contain jewellery from the Punjab royal treasury that has beenmissing.

Since news of the box was first published, tens of people claiming to be descendants of the Punjab royal family have staked their claim to its contents. Sandhanwalia holds that the diamond went to Queen Victoria as part of an annexation treaty that was signed under duress. He says that Duleep Singh, who was eight at the time and under a British regent, was too young to sign a legitimate international document.

Sandhanwalia's claim, if valid, would extend to all the property of Maharaja Duleep Singh that is now owned by the British state, the Queen and various museums here. He told The Times: "Its just a matter of time before I get the box, the Kohinoor and other Sikh treasures belonging to my family that were taken away by the British by force or trickery."

He said he plans to take them back to India and hand them over to Amritsar's Golden Temple, the Sikh's holiest shrine, "where they rightfully belong."

Sandhanwalia has apparently already written to British Prime Minister Tony Blairand to the Queen asking them to hand over his family's property and to "right a wrong". According to The Times, he plans to visit Britain soon to enlist the support of the large Sikh community here.

The 105.6 carat diamond, set in the State Crown of the Queen Mother, is steeped in superstition; it is said to bring ill-luck to the monarch who wears it. Before the annexation of Punjab, successive rulers wore it in an amulet. The Queen also owns the "Timur ruby", a stupendous uncut stone set in a necklace, which once adorned the rulers of Punjab. And, MaharajaRanjeet Singh's ceremonial golden throne is part of the collection of the Victoria and Albert Museum and of the ongoing exhibition of "Arts of the Sikh Kingdoms".