I thought a lot of London Buses had "LT" on them standing for "London Transport", and a lot of them were retained and used on newer buses.
That's correct - there were a few combinations that were reserved for special use, including LT (and later
xLT) for London Transport and PO (later GPO) for the Post Office. Nuffield dealer University Motors in Piccadilly even had an arrangement with the Ministry of Transport whereby they secured "MG" regisrations for the MGs they sold.
London Transport also used to match the numerals form the registration plate in the buses' fleet numbers, so you would quite find that a bus with, say, 69 on the number plate would have a fleet number of 69 (or maybe 169, 269 etc.).
Many of the pre-1963 plates were retained when the old Routemasters were decommissioned, and can sometimes be seen on newer buses. However, I think some may have been "acquired" by London Transport staff; I once saw 3 VLT (at least, I think it was "3") on a car parked outside St James's Park station while it was closed for engineering works, so it presumably belonged to a maintenance worker or supervisor.
Found the following on the web, by the way, so it seems London Transport had special permission to run a ringing operation (as if it wasn't enough that they were allowed to continue using white-on-black number plates into the 1980s
):
"London Transport, uniquely, had a dispensation from the Ministry that allowed them to swap bus identities. It is clear that a bus being out of service for overhaul whilst still taxed would represent a wasted cost. LT therefore adopted the practice of removing a bus’s identity when it went in for overhaul and allocated that identity to a newly overhauled bus, usually the same day."
Further info about this process here:
"The RTs were overhauled every 4 years at Aldenham Works and this involved totally stripping the bus down and separating the body from the chassis. As chassis and body moved down the overhaul "production" line at different rates, it was unusual for the same chassis to be reunited with the same body at the end of the overhaul. But London Transport in addition had a special arrangement with the licensing and taxation authorities. Rather than delicense buses for the duration of their overhauls, registrations and fleet numbers would be taken off buses entering the works and immediately given to overhauled buses leaving the works. Thus when RT overhauls first started, the registrations and fleet numbers disappeared into a "float" until the first overhauled RTs to leave took on the identities of those arriving. These fleet numbers remained out of use until the very last RTs emerged at the end of the RT overhaul programme."
