On Friday, when a debate on Harry Potter started on Twitter about whether Severus Snape was Good, Evil or What? author JK Rowling was luckily at hand to give an explanation on the teacher's character.

Rowling had once said that no story lives unless someone wants to listen , and the author has been engaging with her fans on Twitter throughout about any doubts or questions they may have about their beloved characters.

This is what she had to say on the subject of the potions master and his relationship with Harry Potter: