Game Of Thrones Season 7 Implications: What "The Queen's Justice" Really Means
8. The Question Of The Iron Bank
Apparently because the Iron Bank fear no-one, since riches are the most definitive mark of power in the Seven Kingdoms, Tycho Nestoris turned up to personally demand that Cersei repay her debts, since she is hopelessly outnumbered and cannot hope to win. In other words, she has been classified as a toxic bet and the Iron Bank want their money back.
In reality, Nestoris didn't turn up in Westeros to get his money back - not really anyway. He is there to test Cersei's mettle. He knows the Lannisters have no gold left, so recalling the debt makes no sense. And if he truly believed he wouldn't get his money back, he would have done what the Iron Bank always does, funding Cersei's enemies and making sure she was punished for failing to repay.
In happily accepting Cersei's promise that she would return the gold that was owed, Tycho Nestoris struck a terrible blow for Dany's hopes of victory. After centuries of backing winners, he put his weight behind Cersei, suggesting that even he doesn't believe the odds to be so heavily stacked against her.