It's no secret that Game of Thrones on HBO will deviate from the book. After all the show has, as of last season, caught up with most of the major storylines, and since they haven't stopped filming it's a pretty safe bet that they've made some changes. A new plot point has been possibly revealed by one of the actors. Spoilers below.
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Tycho Nestoris, a Braavosi banker played by Mark Gatiss, may have his story altered from the book. In the book, Tycho is the banker that works with Stannis Baratheon in order to secure a loan from the Iron Bank after Stannis goes to the wall. Tycho also goes to the Wall in order to get "the paperwork" done so to speak.
Gatkiss, in an interview posted by i09, didn't seem to recall filming any events that would indicate that Stannis' story is treated the same way, timeline wise, as it is in the books. When asked, Gatiss replied, "Well, I don't know, I think. . . I think Tycho Nestoris is from later in the books and they've brought him forward a bit. I think I go. . .I go to. . . Do I go to the Wall?"
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Stannis has already met the banker once, back in season four when he's looking for funds to start his war. Without the future meetings, it seems that Stannis' storyline may differ greatly from the books. Perhaps it will be cut altogether or just pushed back into season 6.
Gatiss' made his remarks during the Mumbai Comic Con this year. You can watch the full video below.