Patrick McNee (Steed),Joanna Lumley (Purdey) & Caroline Munro (Tammy) have all appeared in Bond films, A View To A Kill (1985), On Her Majesty's Secret Service(1969) and The Spy Who Loved Me (1977) respectively.
In the very first scene, when Joanna Lumley - Purdey - is in Montmartre Sacré Coeur Paris, everyone in the crowd watches her and the camera. no extras were hired to simulate crowd.