Strong plays Sinestro, a character who is eventually exiled from the Green Lantern Corps in the comic book series and ends up forming his own team of villains.
"Well, famously he's the kind of arch nemesis of Hal Jordan, but in this one he is the greatest of the Green Lanterns and [Jordan's] mentor," Strong explained to DS at the Jameson Empire Movies Awards this weekend. "But everybody knows he goes over to the dark side."
Strong also commented on his character's look being based on that of The Pink Panther actor David Niven, admitting that it was odd to play an alien who has a pencil moustache and a widow's peak.
Watch Mark Strong discuss Green Lantern below:
Additional reporting by Tom Mansell