After a few minutes, the two men made their way to the Green Drawing Room, where two uniformed members of staff had been waiting patiently for several minutes to dramatically open a set of gilded doors heralding their arrival.

About 50 to 60 participants of the Climate Finance Mobilisation Forum, which had met earlier at the nearby Fairmont Hotel, were gathered to brief the two heads of state on their discussions.

The forum was organised by the Government in honour of the King’s legacy on this issue and Grant Shapps, who co-hosted the event, wasted no time in hailing the King’s impressive, decades-long environmental campaign.

The monarch and president stood shoulder to shoulder, smiling as the Net Zero Secretary heaped praise on them for using their convening power to bring together the wealthy business figures and philanthropists who had pledged to invest billions of dollars in climate finance.

Mr Shapps said that the King had been “inspirational” in warning the world about climate change.

He went on: “To you Mr President, we are enormously pleased to see the Inflation Reduction Act doing something we thought we may never see happen in the United States, which is for the world’s biggest economy to join the rest of us in this big journey to get to a cleaner, safer world.”

Mr Shapps warned that if those countries that did not currently have a particularly significant carbon footprint were not brought “up to speed” before the energy transition was solved, it would be too late.

He said that he was pleased to announce that the morning discussions had already resulted in “a couple of billion-dollar pledges”.