London: The British monarchy is facing a legal challenge for the return of the Koh-i-Noor diamond.

The 105-carat stone, said to have been mined in India up to 800 years ago, is set in the crown of the late Queen Elizabeth the Queen Mother, and is on public display in the Tower of London.

However, a powerful cabal of Indian businessmen and Bollywood film stars want it back, claiming the gem was stolen by the British in 1849. The legal action will be potentially embarrassing for the monarchy, as its launch has been deliberately timed to coincide with a lunch hosted by the Queen at Buckingham Palace later this week for Narendra Modi, the Indian prime minister.

The Indian lobbying group has instructed British lawyers to begin proceedings in the High Court to force the Government to return the diamond. Members of the group insist it is an important piece of Indian heritage. The Koh-i-Noor, which means “mountain of light”, was once the largest cut diamond in the world and had been passed down from one ruling dynasty to another in India.

But after the British colonisation of the Punjab in 1849, the Marquess of Dalhousie, the British governor-general, arranged for it to be presented to Queen Victoria. The last Sikh ruler, Duleep Singh, a 13-year-old boy, was made to travel more than 4,000 miles in 1850 to hand the gem to the Queen — a moment regarded by Sikhs in India as a national humiliation.

The British law firm instructed by the campaigners, calling themselves the Mountain of Light group, said it would be seeking to mount its case on the back of the legal principles enshrined in British law that give institutions the power to return stolen art.

David de Souza, co-founder of the Indian leisure group Titos, who is helping to fund the legal action, said: “The Koh-i-Noor is one of the many artefacts taken from India under dubious circumstances. Colonisation did not only rob our people of wealth, it destroyed the country’s psyche itself. “It brutalised society, traces of which linger on today in the form of mass poverty, lack of education and a host of other factors.” Bhumika Singh, a Bollywood actress backing the campaign, said: “Koh-i-Noor is not just a 105-carat piece of stone. It has a lot of history and culture attached to it, and undoubtedly should be returned to India.” The campaign has gained momentum in recent months, winning support from — among others — Keith Vaz, the Labour chairman of the home affairs select committee.

Modi is said to be sympathetic to the rights to the claim, but it is understood that the diamond is strictly off the agenda for this week’s visit. The Government has rejected all demands for the return of Koh-i-Noor, and in 2013 David Cameron, visiting India, defended Britain’s right to keep it.

— The Daily Telegraph