Speaking before greeting Charles and Queen Camilla at a 9/11 memorial event in New York, Mamdani said he would urge the king to return the historic gemstone, which was taken from the Indian subcontinent during British colonial rule in the 19th century.

“If I was to speak to the king, separately from that, I would probably encourage him to return the Koh-i-Noor diamond,” Mamdani said, while adding that the focus of the event remained honoring those killed in the Sept. 11 attacks.It was not immediately clear whether Mamdani raised the issue directly during his brief exchange with Charles, who was seen speaking and laughing with the mayor after the two shook hands at the memorial ceremony.

The Koh-i-Noor, a 106-carat diamond housed in the Tower of London, is among the most prominent jewels in Britain’s Crown Jewels and is mounted in the crown made for Queen Elizabeth the Queen Mother.The gem’s ownership has been disputed for generations.

It passed through the hands of Mughal emperors, Persian rulers and Sikh maharajas before it was ceded to Queen Victoria in 1849 under the Treaty of Lahore following the annexation of Punjab by the British Empire.India has repeatedly sought the return of the diamond, arguing it was taken under colonial rule, though British governments have consistently rejected those requests.

Other countries, including Pakistan, Afghanistan and Iran, have also laid claim to the stone, citing historical ownership ties dating back centuries.The comments quickly drew criticism from Britain’s anti-immigration Reform UK party, whose home affairs spokesman Zia Yusuf described Mamdani’s remarks as an insult to the monarch.

“This beautiful diamond is currently on display in the Tower of London,” Yusuf wrote on X. “That is where it will stay.”Debates over colonial-era artifacts have intensified globally in recent years, with former imperial powers facing growing pressure to return culturally significant objects to their countries of origin.

Charles’ visit to New York included a memorial tribute to victims of the 2001 attacks and meetings with local leaders, amid broader efforts to strengthen diplomatic and symbolic ties between Britain and the United States.