the clue I think is in The city of London, many financial transactions were by word of mouth, but all the paperwork was exchanged between banks ,stockbrokers etc, by messengers, porters, caretakers, housekeepers, the job title varies according to the traditions of the institution.
In a large provincial town in the 60's each bank in the town had a messenger who carried cheques around the town for instant presentation to the originating bank.
one was a housekeeper, two were messengers and one was porter, from personal experience
mike