During an interview on NPR's Weekend Edition Saturday, interviewer Scott Simon remarked to Hugh Grant that before making this movie, Grant and Ben Whishaw had also just worked together on Paddington 2 (2017), and Grant replied, "Well, I mean, it is weird that I have in effect spent the last three years trying to either kill or have sex with Ben Whishaw in one way or another."
On the advice of the director, Stephen Frears, Ben Whishaw met with the real Norman Scott during the course of the production to hear his account of the events.
According to the creative team behind this miniseries, the book upon which the series is based has a naughty, eccentric tone that everyone involved, including screenwriter Russell T. Davies wanted to retain for television. Davies loved the humor but also wanted to immerse viewers in the lives of the characters, giving space to the tragic elements of the real-life story and highlighting the genuine love between Jeremy and Norman.
Hugh Grant has said that eighty percent of his performance was hair and makeup, referring to the transformative work of hair and makeup designer Daniel Phillips. Grant had worked with Phillips previously on the film Florence Foster Jenkins (2016). To achieve Jeremy Thorpe's signature gaunt appearance, Grant actively lost weight through months of intense outdoor cycling. The rest of his physical transformation into Thorpe he credits to the use of brown contact lenses, Phillips' hair and makeup design, and to the costumes of designer Suzanne Cave.
According to series screenwriter Russell T. Davies, when production company Blueprint Pictures sent him John Preston's book as a way to entice him into writing an adaptation for television, he knew within roughly three pages that he would agree to joining the project.