Some people sing for their supper. But the Duke of Sussex (aka Prince Harry) sang for his HIV charity, Sentebale. He and his wife, Meghan, the Duchess of Sussex, attended a benefit performance of the blockbuster musical Hamilton at London’s West End.

At the end of the August 29 performance of the show, Prince Harry joined the cast onstage and broke into song—or was it rap?—specifically, the first line of “You’ll Be Back.”

The show’s creator Lin-Manuel Miranda also attended the performance. He later took to Twitter to note: “King George III’s great-great-great-great-great-great grandson The Duke Of Sussex sang a few bars tonight.”

In case you were on another planet the past several years, Hamilton is a hip-hop musical about Alexander Hamilton and the Revolutionary War. Michael Jibson, who plays King George III in the London production, also tweeted about the surreal meeting with the royal couple.

Prince Harry’s Sentebale charity helps vulnerable children living with and affected by HIV in Lesotho, a small country completely encircled by South Africa, and in Botswana. To read more about this charity and the prince’s HIV-related work, read “A Royal Effort” and “Life Ball 2018.” In case you’ve forgotten who his mother is, check out “Remembering Princess Diana’s AIDS Work 20 Years After Her Death.”

Back in the United States, when Miranda left Hamilton a few years ago, he was replaced by Javier Muñoz, a longtime friend and fellow performer. Muñoz is living with HIV and shared his journey in the POZ cover story “In the Spotlight.”