The term "The Carnaby Street Army" comes from a line in the Kinks song "Dedicated Follower of Fashion".  The lyrics go "Everywhere the Carnabetian army marches one Each one a dedicated follower of fashion" The 1960's in London were a magical and creative time with stars from Mick Jagger and Marianne Faithful to David Bailey and Jean Shrimpton explifying the era with one of its kind style in the history of fashion and music.  This Carnaby Street era was the London sister to New York's Factory scene and San Francisco's Flower Child Scene.  Each scene with it's own unique look and sound.  

Here's "Dedicated Follower of Fashion" by The Kinks to get you in the mood for some London / Carnaby Street vibes: 
dedicated follower of fashion.............the kinks - YouTube