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HELP latin as level translation

Hello! I'm super stuck on a latin translation we have been given as revision, i think I get the gist of some of the sentences but can't work out why some tenses are what they are. It's from Nepos, Hannibal 12-13 adapted. The intro is: the romans finally catch up with their enemy Hannibal when he is the guest of Prusias, king of Bithynia. This is the sentence that really confused me:
Prusias negare non ausus est; noluit tamen a fieri quod adversus ius hospitii esset.

I think the first bit is: Prusias did not dare deny, however he did not want.... I think it's something to do with going against the law of hospitality by doing it himself, but I don't really get how it all works, any help much appreciated!