Peter Firth, Rupert Penry-Jones, Hermione Norris, Richard Armitage, Miranda Raison, Gemma Jones, Hugh Simon and Alex Lanipekun are credited as the main cast.

In December 2007 Penry-Jones announced his intention to leave the series after appearing on the show for four years, because he felt his character had run its course and "getting to the point where I needed to move on," adding he would like to explore other avenues in his career.

[3] Armitage was approached by the producers after he finished work on the second series of Robin Hood in which he portrayed the regular part of Sir Guy of Gisbourne.

The cliffhanger of the sixth series finale, where Jo was apparently killed, was to leave the audience wondering whether she survived.

Lanipekun believed that the seventh series was "kind of for Ben," adding that there was an episode that would see his coming of age by dealing with his first undercover operation and the burden of getting close to someone who is involved with the group he was sent to stop.

Peter Firth, Gemma Jones and Hugh Simon returned as Harry Pearce, Connie James and Malcolm Wynn-Jones, respectively.

They settled on using Russia, which was facing a resurgence in power after the Cold War, which the producers felt, in subtle ways, would threaten the security of the west.

[3] The writers enjoyed making the Sugarhorse storyline because it was one of the instances that "really brings Harry to the edge" and causing him to doubt everything he has done or achieved.

Christian Spurrier noted it was "kind of a headache" to figure out how to "weave it in" to the series and work out what parts would be used in which episodes.

However, by using the small crew, they and the actors generally film the scenes unnoticed by the public, which the producers felt gave the characters such gravitas.

However, the main problem with filming in Moscow was the 30 °C (86 °F)-plus heat, and the actors had to wear winter coats because the episodes were set during the colder months.

Kudos film and television, the production company behind Spooks, had to follow several health and safety provisions from an advisor to ensure the sequence strictly adheres to the advice.

Following the sequence, Armitage stated "I only lasted five to ten seconds, and the sound of my voice crying out to stop isn't me acting.

[23][24] Leigh Holmwood of The Guardian feared that the death of Adam "would have cast a long shadow", but barely noticed his absence given the pace of the episodes.

Holmwood also believed that Lucas's introduction "more than made amends" for replacing Adam, and also felt the return of Ros Myers and her promotion was "a genius move".

[24] Mark Wright of The Stage thought that it was "stunning" with the last three episodes in particular "hitting new heights of tension and storytelling for the series," adding it is "as good as, if not the better, than the first couple of seasons".

Gimmers felt the seventh series performed better than the previous, as it "lost its way slightly" with the concentration of Islamic extremists.

With the introduction of Lucas North, Gimmers stated "the possibilities for double-blinding the audience were legion and every single one was exploited to the max".

[25] David Blackwell of Enterline Media said that the series's storylines "have a grain of truth reflecting today's climate" and also "more deeply rooted in gritty realism and preying on the real dangers that terrorists and other countries pose to the UK".

[26] Following the end of the eighth series, Last Broadcast held a poll for the top five most shocking death scenes in Spooks.

[27] The featuring of an actual waterboarding scene drew criticism from Guardian columnist Zoe Williams, who wrote "it's really unpleasant, [Armitage] concurred.

[29] Because of the strong ratings and positive feedback from fans and critics, the BBC announced they would recommission Spooks for an eighth series for 2009 on 4 December 2008, just days before the finale was set to air.