Movie studios are obsessed with keeping the plots of their latest blockbusters secret.
Stars are sent scripts via encrypted emails that self-destruct Mission: Impossible-style after a few days.
Mobile phones are confiscated on set, scripts are printed on paper you can’t photocopy or photograph and some scenes are even shot near airports to stop drones from spying on proceedings.
Actors have to sign contracts that guarantee confidentiality or they’ll forfeit their first-born child – but sometimes they slip up.
Just ask Karen Gillan, who gave away more than she should about the new Marvel movie Avengers: Endgame at a press conference in California.
As it’s the finale of the 22-movie Marvel superhero cycle, there’s more hype and expectation surrounding this new picture than most.
Gillan plays Nebula, the adopted daughter of arch-villain Thanos who not only tortured her but zapped half of all life in the universe out of existence at the end of the last Avengers outing.
“It’s maybe safe to say she suffers from some daddy issues because her dad is Thanos, so who wouldn’t?” says the Scots star.
“I’m excited for her to face the source of this abuse. This has been building through multiple movies. She’s talked about how she wants to inflict revenge so we all know about that. I’d like to see her try to face that.”
Realising she’d let too much slip by giving away both a major plot point – Nebula and Thanos going head-to-head – and character development – Nebula completes the journey from Marvel villain to hero – the 31-year-old quickly added: “I don’t know if she will! Maybe she won’t. I’m not saying anything. I just got really nervous I gave something away, so I’m going to stop!”
This is the fourth time Gillan, who shot to fame as Amy Pond, the companion to Matt Smith’s Doctor Who, has played Nebula.
And although this is the end of this particular saga, we’re likely to see more of the blue-headed cyborg assassin.
But the 31-year-old from Inverness didn’t think she’d last anywhere near as long.
Gillan admits: “I thought when I signed on for the first Guardians Of The Galaxy movie that I was going to shoot for eight days and then die.
“That’s what it was in the script.
“I had no idea that this was where the character was going.
“Three movies later and there’s three more to come out.
“It’s crazy. But I think it would be really sad to say goodbye. I’ve loved her from the moment I auditioned for her.
“She’s evolved from a villain to someone we’ve developed empathy towards.
“I think she’s going to be a character we’re all rooting for.”
What Gillan, famed for her flowing red locks, didn’t love was having to shave her head to play the smooth-skulled Nebula.
This time, though, camera-trickery replaced the razor and she laughs: “I’ve been negotiating more hair! Some actors negotiate more money, I get more hair and I’m happy with that!
“I mean, they can CGI entire cities so why did I have to shave my head for the first films?”
Avengers: Endgame (12A) is in cinemas now