He's King Charles III, (since 2022). Like Zelensky, he's also a head of state. Unlike Zelensky, he served in the Royal Air Force and the Royal Navy from 1971 to 1976. The King, mindful of his constitutional role, agreed to a meeting, at Zelensky's behest, just as he has issued an invitation to Trump, (both with the agreement, or request of the prime minister).