J.K. Rowling's Harry Potter secret helped Alan Rickman create Snape

Harry Potter creator J.K. Rowling let Alan Rickman into the greatest literary secret of the 21st century when she gave him a clue about how the book series would end after he demanded more information before signing on to play Severus Snape.

The British actor was still considering whether or not to take the role of the mysterious Hogwarts professor when he contacted the author to learn more about the character, and he admits J.K. Rowling gave him the pointers he needed about the end of the books - before she'd completed the seventh novel.

Speaking at the New York Times Arts & Leisure Weekend (07-08Jan12) he said, "I think it's true to say that she had put the ending into a safe right back then. She knew how it would finish.

"There's a lot of speculation about tipping me off about how Snape would end. Before I said I would do it I said I have to talk to her. I rang her up and she was with her sister at the time and said, 'I can't talk now,' so that's how much she kept it to herself; she said, 'We'll talk tomorrow'.

"Then we spoke the next day and she gave me one small piece of information that let me know that there was more to Snape than met the eye. I can't share what she told me because I promised her I never would and I never have."

The information prompted Alan Rickman to sign on - and it gave him the insight he needed to create the "buttoned-up" character.

He adds, "I was very involved in the costume. I was very specific about it. I said the sleeves should be really tight and there should be a lot of buttons because that helped me with the idea that he has to actually be buttoned in... It was very important that... the buttons were tight."