United Kingdom, April 30 -- Kit Harington knew he had to "up [his] game when he was "humiliated" by Bella Ramsey in a 'Game of Thrones' scene.

The 38-year-old actor felt he had complacent playing Jon Snow after six seasons when his then-11-year-old co-star - who plays Lady Lyanna Mormont - tried to give him a prompt when he'd forgotten a line of dialogue.

In conversation for Interview magazine, Bella said: "I don't know whether you remember this, but I remember it quite vividly and have some remorse for it now, but during that scene I was mouthing your lines to you.

"Now I'm like, 'Oh my gosh, how awful.' But at the time it came from a very innocent place of being like, 'Kit's struggling with his line and I know it, so let me just mout...