Ray Austin, appearing uncredited as the "Dead Milkman" was the stunt co-ordinator for the series, and directed some episodes as well.
Roy Kinnear ("Hickey") made a total of four appearances on "The Avengers" (including the final episode), in different roles each time.
Steed and Emma are walking across the base when Emma halts and says,' Look right, look left and look right again'. When they resume walking, the camera pulls back to reveal massive white stripes on the tarmack. An inside English joke. Airbases use those enormous stripes to help approaching pilots see the begining and end of the runways. In English cities pedestrian street crossings are marked with much smaller white stripes (called zebra crossings). Every schoolchild it taught to look both ways before using a zebra crossing.
At about four minutes, as Steed and Emma are walking they cross a bridge, with Emma walking along the wall.. This is the same wall and bridge near the studios that Tara King runs across in the opening sequence of the final series. The location of this bridge is Tyke's Water - used on several Avengers episodes and many films including Taste The Blood of Dracula and TV series including Auf Wiedersehen Pet.
As they near the RAF base Steed describes his groaning men returning from a mission and Emma asks if they had been to the Ruhr. The Ruhr valley in western Germany was the industrial center of the Nazi war machine and a vital target for Allied bombing runs. The Nazi defensive anti-aircraft guns were so thick in the Ruhr that US AAF pilots called the valley Ruhrflaken. Missions to the Ruhr where brutal on flight crews.