The cast of the Avengers: Age of Ultron say the script had to be shredded ever day to avoid details of the movie being leaked. The film's glittering cast attended Tuesday night's premiere in London.

Avengers Age of UltronElizabeth Olsen says security was tight on the set of Avengers: Age of Ultron

Elizabeth Olsen, who plays the new character Scarlet Witch, said security was tight, while Paul Bettany - who plays The Vision - said the script was never emailed to him.

Bettany told Newsbeat that it was posted "with a security guard, with a name all over every page so I couldn't tweet it... it had to be delivered into my hands."

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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, said that most Marvel films are kept under wraps.

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"Everything with Marvel is very lock and key and hush hush, you gotta sign a confidentiality agreement," he said.

Back in February, Sony Pictures and Marvel signed a deal that meant Spider-Man could join the likes of Captain America, Thor and Iron Man in future Marvel releases. Evans suggested there's definitely room for the webbed-one in a future Avengers movie, saying, "As long as he's a good man I think Captain American would accept him."

Avengers: Age of Ultron will hit theaters on Friday (April 24). It has a chance of becoming the biggest grossing movie of all time.