Thanks for clarification. It is odd that in the early days the first few had the then current style of registration, and in a short while were re-registered with their LTZ numbers. I have had a qick search but cannot find any online reference. Can anyone help?
EDIT: I've found a picture of an LT with the registration LT61 AHT.
LT 1-8 were the prototypes, and entered service with the registrations LT61 AHT/BHT/CHT/DHT/EHT/FHT/GHT - LT2 was actually the first in service when it operated a 12.01 Hackney Central - Victoria route 38 extra on 27th February 2012. All eight were subsequently reregistered into the LTZ 1*** series. LT 9-13 initially entered service with Metroline on route 24 with LT13 *** registrations but these were quickly changed to LTZ 10** plates.
And as noted, LT 901-999 carry LTZ 29** plates, whilst LT1000 is LTZ 1000.
New Bus For London - the Inaugural Journey by Julian Walker, on Flickr