I don't know why but I would have thought it unusual for a young man to come down from Scotland and join the Met.
I am not surprised at all. Young men from all over the Highlands moved into Scottish cities and became police officers, so it would be quite reasonable for them to go a bit further south and join a police force in England.
I actually know someone of similar age to myself who did exactly that, and served in the Metropolitan Police for the rest of his career.
It also would not surprise me if someone had studied the topic, but I have no idea how one might find out.