What author citation and abbreviation does (would) a monarch or a crown prince get after publishing a new taxon name?

Even though taxonomic rules appear to be silent about this (I’ve checked ICN Art. 46 and ICZN Art. 51), author citations, as well as abbreviations, are usually based on a surname. However, monarchs and crown princes don’t have surnames per se, at least in the Western culture. Even though they have dynasty names, they may only get referred to by their personal name and dynasty name used as (instead of) a surname after the monarchy was overthrown, and for our purpose let’s assume otherwise.

Has there ever been a case when such a person, while practicing biology (either as a hobby or professionally) published a name for a new taxon and there was a need to make up an author citation/abbreviation? If yes, how was it (they) made? If no, what would be an author citation/abbreviation for someone like, e. g., British Prince William?