Friedrich Schiller wrote this way in Die Kraniche des Ibykus, and the German Bible in Psalm 18:11. It's a bit odd and old-fashioned here. But Harry Potter wants to be old-fashioned, eh?
BUT, you can see this sometimes with separable verbs which carry two prefixes. E.g. umhinkommen:
Sie kommt nicht umhin, solche Seltsamkeiten zu schlucken.
Sie kommt nicht um es hin.
The second sentence refers to the first, and that inserted es representing the whole infinitive clause is in fact even required at this position. It cannot be put elsewhere. It cannot be left out. The verb shatters to pieces.
You can see prefixes, pre- and postpositions and adverbs aren't as distinctive groups as one might think. Often enough these are just different terms for the very same thing.