J.K. Rowling reveals the major clue she told Alan Rickman about Snape's character

After all this time, author J.K. Rowling has finally revealed to fans what was said during a much-speculated private moment between her and Alan Rickman, who died last week, which shaped the way the actor played the iconic role of Professor Severus Snape in the Harry Potter movies.

During the production of the first film, the last four novels had not yet been published and no one but Rowling knew whether or not Snape was truly a bad guy. However, Rickman had previously stated in an RTE interview that during a single phone conversation with Rowling, she had given the actor "one little piece of information" which not only helped convince him to take on the role of Snape for a full decade, but how to better handle the character.

In the same interview, Rickman said he never again had another intimate conversation with Rowling about Snape, and that she had a "hands-off approach" toward the cast's performances. Harry Potter movie producer David Heyman confirmed that Rickman hid the details of his conversation from the rest of the cast and crew during production.

"It was quite amusing, too, because there were times when a director would tell Alan what to do in a scene and he would say something like, 'No I can't do that - I know what is going to happen and you don't,'" Heyman told the LA Times.

Rowling finally provided an explanation Monday morning using just a few simple words on Twitter.

When asked by a fan what she told Rickman, Rowling replied, "I told Alan what lies behind the word 'always'."

"Always," Professor Snape's most famous line, is a symbol for his undying love for Lily Potter, Harry's mother, who was murdered by the series villain, Voldemort. Snape, who always seemed to hate Harry and be allied to Voldemort, was not revealed be a double-agent to readers until the final book, "Harry Potter and the Deathly Hallows." In a pivotal scene, Harry is looking back on Snape's memories after Snape has passed away. After watching Snape and his mother become close in childhood, Harry observes Professor Dumbledore speaking with an adult Snape. Snape then reveals that his motivation for secretly working with Dumbledore against Voldemort, and helping young Harry, was all because of his love for Lily.

Dumbledore asks, "After all this time?" Snape replies, "Always."