Deadpool was only given a definite release date after test footage leaked online and received an overwhelmingly positive response from comic book fans.

Recalling the close relationship he and co-writer Paul Wernick formed with Reynolds and Miller, screenwriter Rhett Reese told AMC show Geeking Out: "We were on set every day. Interestingly, Ryan wanted us there. We were on the project for six years."

"It was really a core creative team of us, Ryan, and the director Tim Miller," Reese added. "Fox interestingly wouldn't pay for us to be on set. Ryan Reynolds paid out of his own money, out of his own pocket."

Made for an estimated $60 million, Deadpool went on to gross more than $780 million worldwide. Fox has given a green light to a sequel, which is due to start shooting in early 2017.