Doctor Who: 10 Clever Moments Of Foreshadowing You Probably Missed

In typical spy movie fashion, Series 12 opener Spyfall was chock-full of misdirection and double-crossing - most notably with the reveal that Sacha Dhawan's supposed good-guy O is actually the latest incarnation of the Master.

While many fans had predicted that Dhawan was playing the Master before Spyfall even aired (he'd been a popular pick to play the Doctor for years), this twist reveal was cleverly signalled within the episode itself, in the surprised reaction of Stephen Fry's short-lived character, C, at the moment of his death.

Right before he's struck with a lethal bullet, C is telling the Thirteenth Doctor about the possibility that corporate big-wig Daniel Barton is a double or a triple agent, working for an evil mastermind. He's unable to finish this thought however, slumping down on his desk after uttering his final word: "Oh."

At first, this seems like a perfectly normal reaction to, y'know, being shot in the neck, but here, the word "Oh" also has another meaning. As we later learn, Barton has formed an alliance with the Master, whose secret spy codename is - that's right - "O".

In other words, C's final utterance works as both a surprised reaction, and an answer to the question of who Barton's villainous overlord could be. Well played Chibnall.