A little history
Yes, I know, it's comedy, and not history. I have no reason to bring history into the movie... BUT...
Sir Knolte says he is "Of Marlborough." There is a Marlborough castle in England. From 1209-1369, it served as a "Dower house," which means that widows of the dead king would live in it. Three kings died during the time Marlborough castle was serving as a Dower house. Henry III Died in 1273. Edward I Died in 1307, and Edward II was murdered around 1327.
The movie is set in 1328, so probably only the last two widowed queens would be alive. Edward II's wife, Isabella of France was apparently engaged in a rather scandalous love affair with lord Roger Mortimer at the time, and would not be spending time at the Dower house, however, Edward I's second wife, Margaret of France might have been around still.
Interestingly enough, Sir Knolte "of Marlborough" is serving an ousted queen. Was Knolte of Marlborough castle, or just the nearby town? Is the ousted queen the dowager, the widow of Edward I, Margaret of France? again, we do not know. After all, Helen Carey's character is never given a first name.
King Leo is trying to marry his daughter to a Duke, a "Norman Duke," as he calls him, or "The Duke of Normandy," or, as the messenger says, "The Duke DuBois." Sadly, there is no known Duke Du Bois. Bois is a french word for forest. However, there was a Duke of Normandy. This is one of the titles applied to the King of England. In 1328, the "Duke of Normandy" would be the 16 year old Edward III, grandson of Margaret of France.
So by the film, we might argue that king Leo had actually ousted the Dowager Queen, Edward I's former wife Margaret of France from Marlborough castle, and was then attempting to marry his daughter off to Margaret's grandson, king Edward III of England... All the while, calling himself a King, and therefore being a pretender to the English throne!
Man, Leo's got some balls of steel, huh?