The Telegraph has a brief article which features a quote from Harry Lloyd. When mentioning that Game of Thrones is “next” for him, Tim Walker goes on to write:

‘An American accent will not required. “It’s an unspoken rule that if you’re American, you can’t hold a sword,” the amiable actor [Harry Lloyd] tells me. “It’ll be like Lord of the Rings. Everyone will do a non-accent. It will be great fun.’