The Star Wars veteran barely appeared in Star Wars: The Force Awakens, and the highly-anticipated mystery surrounding his Luke Skywalker character looks set to be revealed in Episode VIII, which is currently in production.

Mark, who has around 980,000 Twitter followers, has started a campaign to reach one million with the hashtag #HAMILLION and director Rian Johnson has given him permission to let him give Star Wars fans a nugget of information to help his cause.

"Thanks @rianjohnson for letting me reveal 1 SPOILER to try to reach #HAMILLION followers! STAY TUNED! #LeakingLuke," he writes on Twitter alongside a picture of him partially hidden behind a black board emblazoned with the number "8".

He then posted a snap showing the front cover of the script, with "Mark Hamill Highly Confidential" written in large bold type. He adds, "Time 4 a #SWSecret-@rianjohnson OK'd release of stunning #Ep8 plot point-Tell 21,000 friends! #HAMILLION #StayTuned."

It is highly likely that his promise could be a April Fool's Day (01Apr16) prank, as the Star Wars filmmakers like to keep the plot top secret. The Force Awakens director J.J. Abrams didn't trust his cast with scripts to prevent leaks, and actors were shrouded in blankets to stop photographs being taken.

Mark previously admitted he was given a financial incentive to keep the film's secrets, telling, "I have something coming out where there's an amount of money that if it leaks because of me, I don't get that payment... If I keep it a secret until the day it comes out, I get that payment."

The Force Awakens was released in December (15). Episode VIII is expected in 2017.