If there’s one thing I can’t stress enough as a writer and as a viewer, is that you should not have the big surprise spoiled minutes in advance of your episode. Second, what is WITH the whole “Clara tells Bill which ship to take” when it was clearly established in “The Doctor’s Wife” the TARDIS picked Bill and not the other way around. Time can be rewritten? Well episodes can be re-edited, so the whole pre-credits bollocks gets replaced pretty soundly with “Clarence and the Whispermen” and the original sequence is bumped up to the episode’s climax. Yowza!