I am super impressed by all the amazing research, but I am going to run in the opposite direction and bury myself in headcanon. Met on their first day of school. Public school shenanigans with impossibly long summer breaks. Blenkinsop's uncle being a military man (referred by all and sundry as the Colonel) who told them to join up as soon as they finish school because there is a war coming and they shouldn't miss out on any of it. Maltravers not being entirely willing, but someone has to look after Blenkinsop because he is not even remotely capable of looking after himself. Surviving the war and living as "confirmed bachelors" in Blenkinsop's home village. Maltravers chronic insomnia and gutwrenching nightmares. I could go on, but really probably shouldn't at this point.

I HAVE PUT WAY TOO MUCH THOUGHT INTO THIS, OKAY. I AM NOT CHANGING IT NOW JUST BECAUSE OF "CANON".