The cast of the new Avengers film say pages of the script had to be shredded every day on set to stop details of the new movie leaking.
at the Age of Ultron UK premiere, Elizabeth Olsen, who plays new
character Scarlet Witch, said security was strict to prevent hacks.
Paul Bettany, who evolves from voicing Jarvis to becoming The Vision, said the script was never emailed to him.
Bettany told Newsbeat it was posted "with a security guard".
He said it had "a name all over every page so I couldn't tweet it... it had to be delivered into my hands".
Elizabeth Olsen added: "It was quite funny that we had to burn our
sides for the day... we weren't allowed to go home with our little pages
of whatever we shot that day.
"They took it from our trailers and shredded it. It's pretty crazy."
Chris Evans, who plays Captain America, told Newsbeat that most Marvel films are kept secret.
"Everything with Marvel is very lock and key and hush hush, you gotta sign a confidentiality agreement."
Away from script secrecy, Elizabeth Olsen said that Avengers should be watched on the big screen.
"These films aren't plane movies... they deserve to be seen in a cinema the way it was made."
There was a lot of discussion about films being made in 3D on the red carpet as well.
"I think when it's appropriate, when it's the right format, I think it can be great," said Paul Bettany.
films that I've seen in 3D, I then went to see in 2D and I preferred...
I haven't seen this in 3D but I hear that it's extraordinary so I'm
going to stay tonight and watch."
Many characters from the Marvel universe end up in other projects.
Sony Pictures and Marvel signed a deal in February meaning Spider-Man could join up with the likes of Thor, Captain America and Iron Man in future film releases.
Chris Evans said he definitely thinks there is room for Spiderman in Avengers.
"As long as he's a good man I think Captain American would accept him."