Scenes within the Royal household were shot on 35mm film, so they would look lush and cinematic. Scenes 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.
10 Downing Street was portrayed as slightly dilapidated, poorly decorated, and middle-class. This is supposedly how the residence actually was, and the real Cherie Blair was supposedly appalled when she first saw where the family would be living.
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 this movie). According to Peter Morgan, "cabbage" is an actual term of endearment Prince Phillip used for his wife.
Dame Helen Mirren was praised by Queen Elizabeth II and invited for dinner at Buckingham Palace, but could not attend due to other filming commitments at the time.
When Alistair Campbell (Mark Bazeley) asks Tony Blair (Michael Sheen) if he has 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 Sheen.