According to the DVLA web site this is a September 1955 vehicle, un-taxed but with a recent owner change and fitted with a 1489cc engine, colour Brown.
Looking just the same as it did 30 years ago it re-surfaced and was for sale with a classic car dealer and restorer.
As you can see it is ex-Ministry of Defence, Army Transport. Dating from 1955 it's actual use within the Army can only be guessed at, maybe a NAFFI wagon?