Kismet, one of the most luxurious yachts in the world, boasts a helipad, onboard nightclub, full-service spa, and swimming pool. It was designed in Germany by Lürssen Yachts and is adorned with a sculpted jaguar on the bow, a nod to its owner’s Jacksonville Jaguars NFL team.

Shahid Khan, 75, is worth an estimated $13.3billion (£10.9billion) and also owns Fulham Football Club, whose Craven Cottage stadium sits just along the River Thames

A spokesperson for the Mayor said: “Sadiq attended a private event hosted by Shad, who is a friend,” and confirmed that any hospitality received will be transparently declared.

The yacht is expected to remain moored near London Bridge, just a short stroll from the Mayor’s former City Hall base, nicknamed the “Glass Onion”, now under refurbishment following the office’s move downriver to The Crystal in Royal Victoria Dock.

Mr Khan’s appearance on one of the world’s most extravagant superyachts has drawn attention from City Hall critics, with one insider suggesting it was inappropriate.

However, the Mayor’s allies insist the event was a private gathering and point out that the Mayor has long supported London’s role as a global sporting capital, a cause he shares with the billionaire host.

Mr Khan has publicly championed the NFL’s presence in London, backing regular fixtures at Wembley Stadium. He has even called for the Super Bowl to be hosted in the capital, saying it would solidify London as the sports capital of the world.

Shahid Khan’s Jaguars are set to face the Los Angeles Rams at Wembley on Saturday, October 19, with tickets starting at £90.