This is the only episode in which Rhonda speaks. She has the one line "What?", spoken simultaneously with Steed and Tara.
The helicopter seen during the opening sequence is a 1965 Hughes 300 (model 269B) serial number 450189 (registration G-AVZC). It crashed and was damaged beyond repair on March 28, 1990.
First outing for Rhonda Parker as stylish Rhonda, Mother's bodyguard, who will appear silently another 18 times in this series.
MI12 and its obsession with gadgets is obviously poking fun at the James Bond franchise and Q. The gadget-heavy 'You Only Live Twice' was released shortly before this episode aired.
The apparatus that Steed uses to project the photographs onto a screen is called an epidiascope.