Gaffes

William and Dorothy's Marriage Certificate is dated 1989, but the Annulment Certificate for the same marriage is dated 1986.

The movie's title is "The Reluctant Royal", but there are no royals in it. The duke is not royalty, he's just aristocracy. Only members of royal family are royal dukes, and the are referred to as "Your Royal Highness", and not "Your Grace".

At the Ball, Johnny's mother says that she and the Duke last kissed in 1989. That would be 36 years ago (2025). But earlier in the movie, Johnny wants to ask the Duke "Where have you been for the past 38 years?"

It is said that "Beheading was outlawed in the 16th century", but on 9th April 1747, when Simon Fraser, 11th Lord Lovat, was executed on Tower Hill - late in the 18th century.

There is reference to the "Great Northern War". There has never been a war of this description in the UK. There have been a number of uprisings and wars fought in the north of England (including the Wars of the Roses, the English Civil War, and the Pilgrimage of Grace), but not a Great Northern War.

References are made to several British "counts". But there are no Counts in the UK aristocracy: the UK equivalent of a Count is an Earl (though an earl's wife is called a countess).

A marriage certificate issued in Philadelphia would not say "State: Pennsylvania". Pennsylvania styles itself as a Commonwealth, and documents would say "Commonwealth: Pennsylvania".