The film was shot in the actual house on the actual street where the events took place, Gloucester Crescent in Camden Town. Some of the same people still lived there when the star prop arrived, decades later.
Nicholas Hytner told The Guardian that, while filming in Camden Town, the crew arrived on set one morning 'to find the van had been broken into, and that two people had spent the weekend inside it "having a good time with each other". This necessitated the removal of all the van's contents - which had been dirtied up for artistic reasons - to be "deep-cleaned, and then made filthy again".'
At the Hay Festival on 27 May 2015, screenwriter Alan Bennett said "The story told by this film took place 40 and more years ago and Miss Shepherd is long since dead. She was difficult and eccentric but above all she was poor. And these days particularly the poor don't get much of a look in. Poverty is a moral failing today as it was under the Tudors. If the film has a point, it's about fairness and tolerance and however grudgingly helping the less fortunate, who are not well thought of these days. And now likely to be even less so."
During one montage showing the passage of several years, Miss Shepherd decorates her van with Union Jacks and pictures of Queen Elizabeth II. This means it is 1977 (the year of the Queen's silver jubilee).
All the scenes with the character of Alan Bennett interacting with himself had to be staged twice, with Alex Jennings and his double, George Taylor, playing their own and each other's roles so that Taylor's character could later have Bennett's image spliced in over his. Taylor also played a policeman in one of the scenes.
At one point Alan Bennett says he'd rather write about spies than about Miss Shepherd. This is a reference to his plays 'The Old Country' (staged 1977), An Englishman Abroad (1983) and Screen One: A Question of Attribution (1991), all of which are about real or fictitious Britons who spied for the Soviets.
Three of the actors in this movie have starred in the Harry Potter film series: Maggie Smith, Jim Broadbent and Frances de la Tour. However, this is the first time all three actors share the screen outside the franchise.
At one point in the film, Maggie Smith's character Miss Shepherd asks Alan to get her sherbet lemons at the grocery store. In the Harry Potter universe, "sherbet lemon" is one of the passwords for Professor Dumbledore's office. Smith played Professor Minerva McGonagall in the series and had to utter the phrase to allow Harry Potter into Dumbledore's office.
The trivia items below may give away important plot points.
In his introduction to the stage play, Alan Bennett states that Miss Shepherd's back-story is genuine but acknowledges that the character played in the film by Jim Broadbent is invented. (In the play, he is a fellow vagrant and not a police officer.)