Mark Hamill asked Britain's Prince William and Harry to settle a debate about Luke Skywalker's royal status during their Star Wars: The Last Jedi set visit.
Mark's Star Wars character Luke Skywalker is the son of Queen Padme Amidala and Anakin Skywalker, who later becomes Darth Vader. He was adopted from birth and finds out in 1983's Return of the Jedi that he has a twin sister, Leia, who was raised as a princess.
Mark and the late Carrie Fisher, who played Leia, disagreed whether Luke's newfound royal connections made him royal himself, and Mark asked the princes to settle the score once and for all when they visited The Last Jedi set at Pinewood Studios near London.
"I used that opportunity when I met the princes to try to solve something that had been bothering me since Return of the Jedi," he said at the film's London press conference on Wednesday.
"When they told me Carrie and I were brother and sister I said, 'Wait a minute, if Luke is Princess Leia's brother, doesn't that make me royalty? And she immediately said no.
"But when I met the princes I said, 'I really want your opinion on this'… I said, 'My mother was Queen Amidala, my father was Lord Vader, my sister is Princess Leia, doesn't that make me royalty?'"
However, William and Harry didn't give Mark the official verdict that he was hoping for.
"Unfortunately it was a split decision because William said yes and Harry said 'I need more information', so I said 'Darn it. I need the ammunition to rub it in Carrie's nose! It's been going on for 40 years!'"
The royals were pictured on the set of the movie and Daisy Ridley gave them a guided tour of the various prop and creature workshops, although she admits it was "awkward" meeting them at first because she's not great at small talk.
They are said to have filmed cameos as Stormtroopers, something which director Rian Johnson could neither confirm or deny.