The film-makers are going to extraordinary lengths to recreate the marble vaults of Gringotts bank, where Harry is taken by the giant Hagrid. Builders have been busy working behind blacked-out windows for several days. "It's extraordinary the effort going into the scene which really only gets a couple of pages in the book," said a source familiar with the deal. "I suppose there's nothing to say it won't end up on the cutting room floor."