"Oh, I don't mind! You clearly know how to navigate the resources here, and I require no specific qualifications in order to trust in your abilities to assist me."

Shrieky smiled, reassuringly, keeping his tone his tone empty of any inflection which might hint at him understanding that Mycroft didn't want to help him. He glanced towards the rows of books a little idly, before allowing his gaze to creep toward the other man again, "Have you been in Baedel long, by the way?"

Making this conversation polite enough would surely drive them towards a point of critical mass, where the awkwardness of extracting himself from the conversation would outweigh the other man's desire not to help Shrieky.