I looked up the history of the Kohinoor and dont see why the British souverain should not own it. It was stolen more then twice over till it was presented to the British crown, thus I don't see why India should own it.
If you dig a little deeper in history, you will find it was presented under duress, following years of subjugation and enforced rule by the British in vast parts of the Indian subcontinent. In that time, they forcibly appropriateed a number of items of value. To this day, the appropriation of the Kohinoor diamond remains an emotive issue in India.
Extract from Wikipedia:
The
Governor-General in charge of the ratification for this treaty was
Lord Dalhousie. More than anyone,
Lord Dalhousie was responsible for the British acquiring the Koh-i-Noor, in which he continued to show great interest for the rest of his life.
Dalhousie's work in India was primarily aimed at appropriation of Indian assets for the use of the British East India Company. His acquisition of the diamond, amongst many other things, was criticized even by some of his contemporaries in Britain. Although some suggested that the diamond should have been presented as a gift to the Queen, it is clear that
Dalhousie felt strongly that the stone was a spoil of war, and treated it accordingly. Writing to his friend Sir
George Cooper in August of
1849, he stated:
The Court [of the East India Company] you say, are ruffled by my having caused the Maharajah to cede to the Queen the Koh-i-noor; while the 'Daily News' and my Lord Ellenborough [Governor-General of India, 1841-44] are indignant because I did not confiscate everything to her Majesty... [My] motive was simply this: that it was more for the honour of the Queen that the Koh-i-noor should be surrendered directly from the hand of the conquered prince into the hands of the sovereign who was his conqueror, than it should be presented to her as a gift—which is always a favour—by any joint-stock company among her subjects. So the Court ought to feel.[8]Dalhousie arranged that the diamond should be presented by Maharaja Ranjit Singh's young successor,
Duleep Singh, to
Queen Victoria in
1850. Duleep Singh was the youngest son of Ranjit Singh and his fifth wife Maharani
Jind Kaur. Duleep, aged 13, travelled to the United Kingdom to present the jewel.
http://en.wikipedia.org/wiki/Koh-i-Noor