* ActorAllusion: [[Series/RobinHood This isn't the first time]] Lara Pulver has taken [[spoiler:Creator/RichardArmitage]]'s job.
* {{Defictionalization}}: Some terminology and catchphrases invented in this series are now used by the real MI-5.
* EnforcedMethodActing: Richard Armitage was actually "waterboarded" for a FlashBack scene, as a desire for MethodActing. The screams were genuine.
* FakeAmerican: Understandably, quite a few of the CIA personnel depicted on the show are played by British or Irish actors. In fact, Megan Dodds is notable as an ''aversion'' of this by being an American-born actress (albeit one who had been living in London for about five years at that point) playing CIA liaison Christine Dale.
* HeyItsThatGuy: [[spoiler: [[Series/TheSarahJaneAdventures Rani's dad]] works for Indian Intelligence, while Jo Portman [[Series/DoctorWho sang a musical number]] and [[Franchise/StarWars Emperor Palpatine]] is a sleeper agent working as a Chemistry Professor.]] [[Series/{{Sherlock}} The Leak]] in (Series 2, Episode 10 is Sherlock Holmes!
** In only the second episode [[Franchise/PiratesOfTheCaribbean Mr. Gibbs]] is a nasty Fascist [[spoiler: who shoves Lisa Faulkner's head in a deep fat fryer]].
** In Series 1, the head of MI6 is Series/{{House}}!
** [[spoiler:[[TheTudors Edward Seymour]] joining Section D? (Series 9, Episode 1) And so is [[Series/DoctorWho The Girl in the Fireplace]]]]
** [[Series/BuffytheVampireSlayer Giles]] [[spoiler: is a rogue agent who hangs himself]] in Series 1, episode 4.
** [[Series/StrikeBack Terrorist mastermind Latif]] shows up, except that [[spoiler: he's the one being manipulated]].
* PromotedFanboy: Geoffrey Streatfield is a long-time fan of the series, and viewed his role in the tenth series as "a dream role".
* [[ScrewedByTheNetwork/LiveActionTV Screwed By The Network]]: The two cable runs in the US. See the trope entry for more.
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