"It wasn't insincere." His voice was flat and dry, unaccountably irritated that she would think so. He ignored the rest of her statement, as he plainly did hope to gain something. After all, if anyone had the capability to lead a revolution against the idiocy the Ministry perpetrated, it was her and Potter. If he could goad her into actually doing so, all the better.
One eyebrow arched slowly, and he did his best to keep his jaw from setting tight. "I am your client, trésor, and I expect that you will do for me what you would do for any of your clients. I may not be your top priority but I do expect the courtesy of being treated as if I am when I sit in your office. If you find that our past will be an impediment, perhaps you would prefer that I request another accountant?"
He knew it wouldn't look good for her record if he did, but it wasn't a threat, either. If he couldn't trust her to look out for his interests, she had no business being in a position to do so.
He held her gaze and refrained from reminding her that if it weren't for her own interference in his fate, he likely wouldn't be here in the first place. But he could allude to it, stating quietly, "You have always done the right thing when there was a right thing to be done, trésor. I expect you will do so again."