Zohran Mamdani urges King Charles to return 'infamous' diamond to India — the only major US official to do so. What's this all about?

"If I were to speak to the King separately from [the purpose of the event], I would probably encourage him to return the Koh-i-Noor diamond," Mamdani said ahead of the event (3).

A priceless asset

The 105-carat Koh-i-Noor diamond has passed through empires for centuries, becoming a symbol of power under Sikh ruler Ranjit Singh in the early 1800s (4). Officials have described the diamond as a "valued piece of art with strong roots in our nation's history," Reuters reported (5).

Now, India continues to press for its return, arguing it was taken during colonial rule and remains a culturally significant asset. The government has formally requested its repatriation multiple times since independence in 1947 (6) — including again in 1953 — but those efforts were rejected.

Now part of the British Crown Jewels, the diamond is on public display at the Tower of London, which attracts more than 3 million visitors each year. A study by luggage storage firm Bounce (7) estimates the tourist site ranks as the world's 14th highest-earning tourist attraction, generating about £68.7 million (8) — roughly $93 million USD — in annual revenue.

The stone — roughly the size of a hen's egg — is set in the crown that was worn by Queen Elizabeth The Queen Mother during the 1937 coronation of King George VI (9) and later at the coronation of Queen Elizabeth II.

While it has no official price tag, estimates suggest the diamond could be worth anywhere from $140 million to $400 million (10), though many experts argue its true value is effectively priceless given its rarity and historical weight.

That's what makes the debate so sensitive. Returning the diamond wouldn't just be symbolic, it could open the door for broader claims over valuable artifacts held by governments and institutions around the world. Former prime minister David Cameron acknowledged that risk in 2010.

"What tends to happen with these questions is that, if you say yes to one, you suddenly find the British Museum would be empty," he told New Delhi Television (11).