dailykitharington:

Some of the actors who are playing smaller roles in the show initially came to our attention because they read for the part of Jon Snow. We looked at many people, and Kit Harington really, really stood out. He was one of the strong contenders, right from the first. He had a great look for the character. His performance was wonderful. Prior to that, his biggest thing was the British stage play called War Horse, which I believe has just come to Broadway as well. He was very acclaimed in that, and we knew about that. He was a fabulous find for us. - George R.R. Martin