The Prince of Wales will represent the COP30 climate summit in South America next month, as announced by palace sources.
The father and son duo appeared together on Thursday night at a event leading up to the environmental conference, which is set to be held in the northern Brazilian city of Belem.
Father and son were in attendance at the museum gathering, marking an unusual joint appearance at a environmental conference preliminary meeting arranged together with the UK government.
King Charles has been a consistent supporter of environmental conservation - and the Prince of Wales has taken on the baton, with his own climate innovation awards, which will be held in Brazil preceding the COP summit.
Royal sources have portrayed Prince William's attendance at the next COP as assuming an significant responsibility in "environmental negotiations".
The monarch and his heir, making a joint entrance in the official car, were welcomed attendees such as environmentalists, scientists, environmental activists, foreign representatives and government officials.
This participation featured addresses in concert with French leader Macron of the French Republic and other global statesmen at the Blue Economy and Finance Forum in the Principality of Monaco earlier this year.
The UN meeting will dovetail with the prince's own sustainability recognition program, which will conclude in Rio de Janeiro the eve of he joins the climate conference on November 6th.
In recent days the prince referred to the Earthshot finalists as "modern-day pioneers".
The monarch has been a key figure at earlier environmental conferences, providing the introductory remarks in Dubai for the 28th Conference of Parties, including the statement: "We are custodians of the planet, not its owners".
"Throughout my life I've dedicated a substantial portion of my life trying to warn of the critical dangers confronting humanity over planetary heating, environmental shifts and ecological decline," the sovereign addressed attendees.
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