According to Jon Pertwee, Roger Delgado was afraid of the water and it took great courage for him to film the scene in which the Master and the Doctor are rescued from the sea by the Navy. However, Delgado's widow Kismet says this is untrue and that he was actually worried about getting his costume wet, as there was no spare available.
This episode was watched by 8.5 million viewers on its original transmission.
First of two Pertwee serials that John Caesar has minor roles in.