The trailer as already pointed out, has an Army census number dating from around 1944, give or take a year I would think. Trailer was part of a contract for 5 ton, 4 wheeled General Service cargo type and made by Eagle Trailers. From looking at the body work details, I would say this trailer has been rebodied to house the ex-RAF generator, but from the view of the rear, I would doubt it was converted for the military, my thoughts are perhaps for the Post Office Telephones, BBC, etc. The plate showing P & S Motors of Teddington..................they would appear to be still in business, maybe someone there could throw light on this, I am guessing that it was rebodied by them for its new role in the 1950's.