After the war, Philip was granted permission by King George VI to marry Elizabeth. Before the official announcement of their engagement in July 1947, he abandoned his Greek and Danish royal titles and became a naturalised British subject, adopting the surname Mountbatten from his maternal grandparents. He married Elizabeth on 20 November 1947. Just before the wedding, he was created Baron Greenwich, Earl of Merioneth and Duke of Edinburgh. Philip left active military service when Elizabeth became monarch in 1952, having reached the rank of commander, and was formally made a British prince in 1957.