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.
Helen Mirren, who plays the Queen, is of Russian ancestry. In real life, it is Prince Philip who is connected to Russian royalty, through his father he is the great-great grandson of Nicolas I of Russia and his maternal grandmother was the eldest sister of Tsarina Alexandra Romanov, the last Tsarina of Russia.
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.
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.
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.
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.)
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.
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?"
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.
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.
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.
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.
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.