The actual term King's or Queen's English actually refers to a type of speech known as Received Pronunciation.
“Oh, an Irish—American?”
“If you heard him talk you would not doubt it. Sometimes I assure you I can hardly understand him. He seems to have declared war on the King’s English as well as on the English king."
Bob's your uncle.
Nowadays, speaking with that accent can have negative social consequences.
Cameron's finding his Etonian vowels