When asked what she did in Poland Elizabeth replies casually that she was in a travelling circus. The 'Circus' was John le Carré's (made up) name for the British secret service.
On the BBC, author Richard Osman said he would be having nothing to do with the production because producer Steven Spielberg made E.T., l'extra-terrestre (1982) and if he did that he knows how to make a film. He said this was the first of four books featuring the characters in The Thursday Murder Club. The second, The Man Who Died Twice, was released in September 2021.
Ingrid Oliver who plays Joyce's daughter Joanna has been married to the book series author Richard Osman since 2022.
In one scene, Stephen tells Elizabeth that she "looks like the Queen". Helen Mirren (who plays Elizabeth) had previously played Queen Elizabeth II in The Queen (2006). Jonathan Pryce (who plays Stephen) had previously appeared as Prince Philip, Duke of Edinburgh in the fifth and sixth seasons of The Crown (2016).
In the novel, Joyce mentions the idea of watching a re-run of Suspect numéro 1 (1991) on TV. Helen Mirren (who plays Elizabeth in the film) had starred as the lead in that series.