When Lady Pembroke first discusses Dr. Willis with Pitt, Pitt reaches out for Lady Pembroke's note twice.
George III is depicted wearing a wig, something the actual King George III refused to do.
In the film, all the daughters of George III and Charlotte are portrayed as young children. However, in 1788 the daughters were ages 22, 20, 18, 12, 11, and 5.
Pitt and Thurlow go to visit the King at Kew during the winter - but the leafy green trees outside clearly indicate that the scene was filmed in summer (shooting took place from July to early September).
At the end of the film, the Royal Family goes to Saint Paul's Cathedral. A view of the front of the Cathedral shows that the clock in the left-hand tower is missing, but this was as a result of German bombing raids in the early 1940s.
A globe shows post-1846-but-before-1848 United States boundaries, including the Louisiana Purchase and Oregon Territory, but with California and Nevada (among other territories) still Mexican.
In the very first shot, the door of the antechamber that Greville knocks on has the date 1862 carved into it (on the left-hand side).