"Very well. Follow my associate so that we can get these debts settled," said the goblin.
Harry nodded. He did not lower his guard, because this was actually a risky gamble. Wizards weren't the only ones that knew of time travelers. And there were easy ways to pick up on time travelers.
Too bad Harry had something most of them didn't.
Common bloody sense.
With the use of a wandless memory charm, and writing a diary that had the counter charm on the first page, Harry was relatively sure he could skate by whatever the goblins used to detect people like him.
Sure enough, the goblins were quick to test him for time travel, and aside from having to show off his "mother's" time turner, they came up empty. And he had walked into Gringotts with his briefcase, so they couldn't bust his knowledge of how to make or use pocket dimensions.
Without any proof of time travel, they had to honor the contract Harry had brought with him.
Quite a few Death Eater and old families were going to be in for a nasty surprise the next time they went to bribe their way out of prison.