I'm from the era when the registration of a Routemaster and the stock number
matched. For instance I seem to remember something along the lines WLT885
was RM (or was it RML) 885.

But over the years, some Routemasters seem to have acquired new
registrations. Now, I can understand that when sold on from LT they might
have received new registrations but is it that simple and why did LT not
sell with the registrations, was it because of the "exclusivity" of the LT
in WLT, VLT etc?