Dr Nathan Ross, a former deputy high commissioner to Papua New Guinea, will act as an assistant private secretary to the new King, the Daily Mail has reported.
According to Ross' LinkedIn profile he joined the Private Secretary's office last month.
The office acts as the primary source of advice to the King for constitutional, governmental and political affairs, and Ross will be advising King Charles about sustainability.
Ross was formerly with the Ministry of Foreign Affairs and Trade, where he joined as a climate change specialist.