The royal visit of King George V to Downton Abbey was based on his real-life visit to Wentworth Woodhouse, a mansion in Yorkshire which was used in this movie for the ballroom scenes at Harewood House.
The mansion that King George V and Queen Mary visit after Downton Abbey, where the ball is held at the end of this movie, is Harewood House. Although the name of the village is pronounced as it is spelled (Hare-wood), the House and the title Lord Harewood are perversely pronounced Harwood, as was correctly done throughout this movie.
According to the Director's Commentary, Charlie Watson (Albert the Hall Boy) originally featured as a reoccurring extra in series 5 & 6 of the television version of Downton Abbey (2010). The film version marks Charlie's first role with lines. Director Michael Engler said that "it felt in a funny way similar to the story; which is the Hall Boy who becomes the Footman - it's like the extra who becomes an actor".
The series began in April 1912 with news of the sinking of the Titanic. This feature film takes place 15 years later. During that entire time period, King George V was the reigning monarch. He was not expected to become the monarch when he was younger since he had an older brother, Prince Albert Victor. When his older brother died at 28, he then became next in line for the monarchy. His second son was not expected to become King either but ascended the throne when his infamous older brother, Edward VIII abdicated and made him King George VI, father of Queen Elizabeth II.