Oh, what lovely finds! Thank you for your digging! : D

and FotH got a glowing letter to the publisher from a historian descended from the MacDonells of Glengarry; no wonder Broster felt the need to diguise 'Pickle' Glengarry under a fictionalised identity in the two later books!
Did you find that glowing letter? I'd love to read it. And ha, that could indeed be a reason to fictionalise Pickle the spy!