The scenes within the Royal household were shot on 35mm film, so they would look lush and cinematic, while those within Blair's world were shot on 16mm, so they would look more like television, in order to give visual contrast between commoners and royalty.
When she was interviewing people who knew the Queen personally, Helen Mirren discovered that the Queen suffers from obsessive compulsive disorder. It was her idea to show the Queen putting pens in order on the table while talking to Tony Blair on speaker phone at Balmoral. Director Stephen Frears was not convinced at first, but thought it worked quite well with the finished film.
Some aspects of the characters are known to be true to their real-life counterparts. Cherie Blair's hostility to the monarchy has been widely reported, including her refusal to curtsy (said to amuse the Queen in private, as it does in the film). According to Peter Morgan, "cabbage" is an actual term of endearment Prince Phillip uses for his wife.
Tony Blair, who claims he had never seen the movie, was suspected of stealing from the movie when he wrote his autobiography, "A Journey". In the scene where he and the queen meet for the first time, Elizabeth says, "You are my 10th Prime Minister, Mr. Blair. My first, of course, was Winston Churchill." Peter Morgan has said that he completely made up the dialog for the scene and it is unlikely he guessed such a specific line exactly right.
Helen Mirren says transforming herself into the Queen came almost naturally after the wig and glasses, especially since she shares a default facial expression, a slightly down turned mouth, with the monarch. She also regularly reviewed film and video footage of Elizabeth and kept photographs in her trailer during production. The writer Peter Morgan says it was convincing enough that, by the end of production, crew members who had been accustomed to slouching or relaxing when they addressed her were standing straight up and respectfully folding their hands behind their backs.
When Alistair Campbell asks Tony Blair if he's seen the day's papers, Blair sarcastically replies, "No, I thought I'd give 'em a miss today. Of course I've seen the papers!" This line was improvised by Michael Sheen.
10 Downing Street was portrayed as slightly dilapidated, poorly decorated, and middle-class. This is supposedly how the residence actually is, and the real Cherie Blair was supposedly appalled when she first saw where the family would be living.
Helen Mirren arranged for the actors playing members of the Royal family, specifically James Cromwell, Sylvia Syms and Alex Jennings to spend a lot of time together off camera. This was done so that they would feel comfortable with each other like a real family.
Large parts of the film are real life; it includes several of Diana's real press conferences, scenes from outside Buckingham Palace after the death of Diana (including those of flowers, and the hysterical population taking interviews), and scenes from her funeral. Therefore, many of the uncredited appearances are from Princess Diana, several broadcasters and many celebrities from the funeral (including Elton John, Nicole Kidman, Tom Cruise, Steven Spielberg and so on).
The writer Peter Morgan reconstructed the events of the week after the death of Princess Diana through extensive interviews with many unnamed sources close to the Prime Minister and the royal family. Many of these sources were able to corroborate the accounts of others, giving Morgan enough information to imagine intervening scenes.
Writer Peter Morgan's favorite line is after the Queen has taken the final call from Tony Blair in the kitchen at Balmoral. She hangs up the phone, heads upstairs, knocks on the door, and simply says, "Mummy?"
The jewelry Helen Mirren wears is based on actual jewels owned by Elizabeth II. Some pieces shown include: her trademark 2 or 3 strands of pearls, Queen Victoria's bow brooch (at Diana's funeral), and Queen Mary's button earrings (the large pearl earrings each topped by a tiny diamond.)
One of the biggest single costs of the film was using a helicopter to fly over the stalking party to get a view of the Scottish countryside. Director Stephen Frears was in the helicopter to get the shot, and was sick with the flu at the time. Regardless, he thought it was worth it to obtain such gorgeous scenery for the film.
While driving in the SUV at Balmoral, Charles asks the Queen, "Why do they hate us so much?" The original reply from the Queen was to correct Charles by saying, "You." Helen Mirren asked to cut the line, and it was changed to the more subtle, "Not 'us,' dear."
Helen Mirren, who plays the Queen, is of Russian ancestry. Both Queen Elizabeth II and Prince Philip are connected to Russian royalty: Tsarina Maria Feodorvna, wife of Tsar Alexander III and mother of the last Tsar Nicholas II, was the elder sister of the Queen's great-grandmother Queen Alexandra and King George I of Greece, grandfather of Prince Philipp. Furthermore, he is also the great-great grandson of Nicholas I of Russia and his maternal grandmother was the eldest sister of Alexandra Romanov, the last Tsarina of Russia, who in turn is a first cousin twice-removed of Queen Elizabeth.
Both director Stephen Frears and writer Peter Morgan were out of the country the week that Princess Diana died. Morgan claims to have been getting married at the exact time that the Princess's funeral was taking place. Both men feel that being geographically removed from that highly emotional week in Britain better prepared them to work more objectively on the film.
The Lord Chamberlain tells Tony Blair that "representatives of all three palaces" will be attending the meeting to discuss plans for Diana's funeral. The three palaces mentioned in that line refer to Buckingham Palace (the Queen's residence), St. James's Palace (the residence of the Prince of Wales), and Kensington Palace (the base of operations for Diana's staff).
The film portrays Charles as being terrified of being shot. In reality, he supposedly was, even going so far as to deliberately leave notes to himself saying as much, where his staff might find them. This activity was filmed but cut from the final movie.
The five corgis who portray the Queen's dogs won the 2007 London Film Festival's first-ever Fido award for dogs in movies. They won "Best in World" and the "Best Historical" category. They are owned by Liz Smith, a retired UK caterer, and were "discovered" by a film scout at an obedience competition. Their names are Alice, Anna, Megan, Oliver, and Poppy.
Director Stephen Frears chose to film the Queen crying quietly to herself from behind her, as he felt that royalists would be uncomfortable seeing the Queen portrayed in such an intimate and emotionally vulnerable state. He then threw in a little joke for the ladies by depicting the Queen rubbing her wet eyes and nose on an extraordinarily expensive scarf.
The film makes a couple of references to Alice in Wonderland. E.g, The Queen Mother thinks Tony Blair (played by Michael Sheen) has a Cheshire Cat grin. Although he didn't play the Cheshire Cat in Tim Burton's Alice in Wonderland (2010), Sheen did voice the White Rabbit.
Helen Mirren was the star of the television series "Prime Suspect," in which she played a Detective Chief Inspector who was the first woman to hold that job in her district. In the first episode, when one of her employees struggles with what he should call her, Mirren's character says, "I don't like Ma'am--I'm not the bloody Queen."
In 2015, Helen Mirren again portrayed Queen Elizabeth II, this time in the Broadway play "The Audience". Mirren won the Tony Award for this portrayal of the queen, making her the tenth performer to win both awards for portraying the same person or character, and the first since Lila Kedrova won both awards 31 years earlier.