Peter Jeffery appeared in both The Avengers and The New Avengers.
The opening scenes were filmed in the old 32 Squadron Headquarters on the Southside of RAF Northolt.
During Steed's interrogation of the Bishop's driver, graffiti can be seen written on the walls of the room. One is 'Leon Davis slept here'. Leon Davis was the construction manager in the art department of this production.
The women in the photos that Jo asks Steed about are former Avenger actresses. Honor Blackman, Diana Rigg and Linda Thorson who played Cathy Gale, Emma Peel and Tara King respectively.