Question 2 - Did British banks really keep track of all the five pound notes by serial number that came through?
This one is a Josephine Tey novel written in 1929.
"Over their dinner Grant decided that in the morning Williams should visit the banks in the area indicated by the letter's postmark, and with that as a basis, track down the history of the bank-notes [5 at 5 pounds each]. It shouldn't be difficult; banks were always accommodating."
I mean, I assume she didn't just make that up, but wow! All notes? When did they stop?