(IDEX Online) - The iconic Koh-i-Noor diamond is again threatening to sour relations between India and Britain, with the prospect of Queen Consort Camilla wearing it at the forthcoming coronation, next May.The 105.6-ct D-color stone was "surrendered" by the last Sikh ruler of India, the Maharajah of Lahore, when Britain annexed the Punjab in 1849. India has been demanding its return since the country was granted independence from Britain in 1947.Indian Prime Minister Narendra Modi's governing BJP party has warned that using it in the coronation could "transport a few Indians back to the days of the British Empire".A party spokesperson told The Telegraph newspaper: "'The coronation of Camilla and the use of the crown jewel Koh-i-Noor brings back painful memories of the colonial past."Queen Elizabeth II, said shortly before her death that Camilla, second wife of Prince Charles (after Princess Diana) would become queen, and indicated that she would wear the platinum crown in which the Koh-i-Nor was set in 1937, together with another 2,800 diamonds.However there is growing pressure against such a move, and speculation that Camilla could wear the crown - minus the removable Koh-i-Noor - at the coronation.Pic shows the Koh-i-Noor diamond loose, and set in Queen Elizabeth's crown