Stephen Lister, the writer, was an 18-year-old fan of the show who sent the script for this episode to the production team and, against all odds, it was promptly accepted.
In the scene where King's car is blown up, a nearby rubbish skip has some graffiti scrawled on it: "Dennis Abey Rules OK". Dennis Abey was the director of the episode.
Bodie has a photo of Cowley's face in the centre of the telephone dial in the scene where he finds a bomb inside the phone.
After Bodie and Doyle defuse the bomb inside the telephone, Bodie says to Doyle "Make someone happy" in reference to the phonecall he was making. This references the GPO's telephone advertising campaign at the time, which used the slogan "Make someone happy with a phonecall".
During the interior establishing shot of the hospital, an announcement is heard calling for "Mr Lewis". This was the name Lewis Collins was known as during his time as a hairdresser at the Andre Bernard Salon, Liverpool.