FYI: the most recent article on this in The Times states that the late Queen in her earliest statement on the surname stated it as being "Mountbatten-Windsor". But in the many years since, it seems to be omitted in all or most use by her descendants, and not just Andrew. The royal office sounds as though they have not made any official final decision going forward, and if Andrew in fact must now use the hyphenated version then...so must his daughters, so must his niece/nephew or others currently using same.