Days after New York City Mayor Zohran Mamdani sparked a viral firestorm by singling out Citadel founder Ken Griffin—filming a pied-à-terre tax announcement video directly outside Griffin’s $238 million Manhattan penthouse—Mamdani set his sights on a slightly bigger target: the British monarchy.

Speaking at a press conference on Wednesday, Mamdani said that if he had a private audience with King Charles III—who was in New York as part of his U.S. tour—he would urge the monarch to return a Crown Jewel to India. “I would probably encourage him to return the Koh-i-Noor diamond,” Mamdani said. The comment came just hours before Mamdani met the King in person at the National 9/11 Memorial & Museum, where Charles and Queen Camilla were paying tribute to victims of the 2001 attacks as part of a four-day U.S. state visit.

Images captured at the public ceremony showed the mayor and King exchanging a handshake, though neither Mamdani’s office nor Buckingham Palace disclosed specifics of their conversation.

The Koh-i-Noor is a 105.6-carat gem that the East India Company took from a deposed Indian leader—10-year-old Maharaja Duleep Singh—in 1849. The stone has since been mounted in the crown of Queen Elizabeth and remains part of the Crown Jewels, on display in the Tower of London. India, Pakistan, Iran, and Afghanistan have all at various points laid claim to the diamond, and the British government has consistently declined to return it.

The Koh-i-Noor remarks landed less than two weeks after Mamdani’s clash with Griffin dominated New York political headlines. On April 15, the mayor released a 60-second Tax Day video promoting a new pied-à-terre tax, New York’s first, that proposes an annual fee on residential properties worth more than $5 million whose owners do not live in the city full-time. Mamdani filmed the video directly outside Griffin’s record-setting penthouse and called the hedge fund billionaire out by name, saying the tax would fix “a fundamentally unfair system.” “These units are sitting empty,” he said. “And even so, they’re able to reap the huge financial rewards of owning property in, dare I say, the greatest city in the world.”

Citadel fired back, calling the video “shameful,” while Griffin himself called it a “personal attack” that displayed a “profound lack of judgment.” Citadel’s COO Gerald Beeson suggested that it might scrap a projected $6 billion redevelopment of 350 Park Avenue in a letter to employees following the video.

The juxtaposition of taking on both a Wall Street titan and a European monarch within the span of two weeks is consistent with Mamdani’s political brand since his history-making Nov. 2025 election win, in which he defeated independent former New York Gov. Andrew Cuomo and Republican Curtis Sliwa to become the city’s first Muslim and first South Asian mayor. The pied-à-terre tax alone is projected to generate at least $500 million for the city.

Whether needling King Charles about colonial-era diamonds moves that agenda forward is another question. For now, Mamdani appears content to let the moment speak for itself.

For this story, Fortune journalists used generative AI as a research tool. An editor verified the accuracy of the information before publishing.