"F—king hell! Sorry guys!" That's what Maisie Williams said, more than once, while filming her big Game of Thrones battle.

"I think I probably hold the record for the most apologies on set," Williams said when discussing her long battle with White Walkers inside the Winterfell castle.

In the behind-the-scenes video below, Williams and the Game of Thrones crew detailed all the work that went into Arya's heroic day at Winterfell. Williams said she was told to start training a year before it happened.

"Maisie does almost all of this stuff on her own," co-creator David Benioff said about Williams' fight scenes. "She has an excellent stuntwoman for the dangerous stuff, but most of it is actually Maisie."