Not surprisingly, it sounds like it was those rather Shakespearean elements of the comics that appealed to him most: "To work on a story about one of the immortals, Gods, extraordinary beings, inter-dimensional creatures. There's science fiction and science fact and fantasy all woven into one. It's based on Norse legends which Marvel sort of raided in a brilliant way ... It's a chance to tell a big story on a big scale. It's a human story right in the center of a big, epic scenario."
He refused to comment on all things casting and Kevin McKidd, though: "There's been lots of talk [about casting] - I sound like a politician - but we are too early at this stage. We're getting the story and the visual effects together and all of that is very exciting. Someone sensational is going to play the part but it is early days."
I'm still weirdly optimistic about this choice -- you couldn't have mentioned a Thor movie to me, Matthew Vaughn helming or not, without my snickering ... but Branagh's flair for the dramatic says this Thor will be hugely entertaining. I freely admit that could be in a bad way, but hey, ambitious failure is almost as much fun as epic success. The Son of Asgard deserves no halfway effort.