Helen Mirren's performance received a five minute standing ovation at the film's premiere at the Venice Film Festival.
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.
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.
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.
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.
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.)
Nathan Larson, who had composed the score for the previous film in the series, The Deal (2003) (TV), had his score replaced by Alexandre Desplat after Stephen Frears found the first score not suitable. Desplat finished his score in three weeks.
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).
Joan Plowright was offered the chance to play The Queen Mother.
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 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.
The real Queen Elizabeth II refuses to watch this film, as she does not wish to relive "one of the worst weeks of her life."