Kingsman: The Secret Service 2: Matthew Vaughn reveals how Colin Firth might return

Firth has not ruled out a return as spy Harry Hart in the developing sequel

Colin Firth as Harry Hart in Kingsman: The Secret Service (20th Century Fox)

Hit spy movie Kingsman: The Secret Service is heading for a sequel but whether or not its lead star will be returning remains in doubt.

Colin Firth starred as a gentlemanly yet kickass agent in Matthew Vaughn's fast-paced adventure earlier this year, alongside Taron Egerton as his promising street kid protégé Eggsy.

It has now emerged that a follow-up is in the pipeline with the cast yet to be confirmed, The Wrap reports.

Look away now if you are yet to see the first film, but those of you who have will know that Firth's character Harry Hart is killed, a plot detail that clearly poses some problems.

“A lot of people are very upset that Colin might not be in the sequel,” Vaughn told USA Today. “But I'm coming up with ideas at the moment. If people buy tickets in America I've got a feeling we'll figure out a way for having Colin back.

“The opening of Kingsman 2 will have a sauna and the sauna door opens and out comes Colin. It was all a dream!”

Sequels are dominating the 2015 movie slate but Firth maintains that follow-ups are okay, so long as they are good. “If it feels like you’re trying to squeeze something more out when it’s expired then that’s deathly, but they can work if they’re a developing series that stays fresh,” he told The Independent in January.

Kingsman recently passed the $400 million milestone at the global box office and is the highest-grossing film of the year in South Korea so far, where it has earned more than $45 million.