I think that the London shot was taken in several days. The team managed to block the areas where they were shooting and they only has some minutes to do their work. From what I know, they did this very early in the morning to avoid traffic issue... and also, lighting was a huge challenge to get the scene as we watch it in the film. Please, take a look into my very last post which also is related to films, I would like to talk to you about movies.