MONTE-CARLO, MONACO - MARCH 18: Prince Serge of Yugoslavia and his wife Eleonora of Yugoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco. (Photo by Pascal Le Segretain/Getty Images)

MONTE-CARLO, MONACO - MARCH 18:  Prince Serge of Yugoslavia and his wife Eleonora of Yugoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco.  (Photo by Pascal Le Segretain/Getty Images)

MONTE-CARLO, MONACO - MARCH 18: Serge of Yougoslavia and his wife Eleonora of Yougoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco. (Photo by Stephane Cardinale - Corbis/Corbis via Getty Images)

MONTE-CARLO, MONACO - MARCH 18:  Serge of Yougoslavia and his wife Eleonora of Yougoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco.  (Photo by Stephane Cardinale - Corbis/Corbis via Getty Images)

MONTE-CARLO, MONACO - MARCH 18: Serge of Yougoslavia and his wife Eleonora of Yougoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco. (Photo by Stephane Cardinale - Corbis/Corbis via Getty Images)

MONTE-CARLO, MONACO - MARCH 18:  Serge of Yougoslavia and his wife Eleonora of Yougoslavia attend the Rose Ball 2017 To Benefit The Princess Grace Foundation at Sporting Monte-Carlo on March 18, 2017 in Monte-Carlo, Monaco.  (Photo by Stephane Cardinale - Corbis/Corbis via Getty Images)