The series was commissioned by BBC Fiction's controller Jane Tranter as a spin-off of their long-running drama Spooks, offering a "more maverick, younger perspective" that would attract a 16-24-year-old audience. The series follows a group of six new young MI5 recruits who "follow a different rule book".

The decision to relate the new project to the original Spooks was controversial, with actor Georgia Moffett saying “it’s slightly misleading in terms of the word Spooks.” and producer Chris Fry saying "this is a completely new show. There are no crossover characters or storylines and, most importantly, it is set in a completely new world." After the relatively unsuccessful first series, executive producer Karen Wilson claimed that many of the existing cast members were "contracted for another year" and outlined themes "we'd like to explore if we get a second series."