When Steed halts his Bentley after the electrocution on live TV, the camera zooms in on Steed, but the background projection remains the same.
Not only does Steed have an obvious stunt double in the dueling scene, the double holds his left hand in front of him, which is something no trained duelist would ever do.
When Mrs. Peel is looking in Cartney's appointment book, it is dated January 1966. Also, in the same scene, Cartney writes out a check for "one thousand guineas only" yet writes "1050" in the following box.