The AEC with the demountable body was an ex WW1 "Y" type used by the Great Western Railway on one of the developments of the "Stand Dray System". The date is early to mid twenties and the idea was then (just as it is today) to use demountable bodies to speed the trucks on their way. The empty bodies were placed on old horse drays for loading and then winched across onto the truck. The basic idea was to replicate the speed at which a horse could change between empty and loaded drays. In fact the system shown was not too successful, but variations on the theme continued for many years on the larger rigid vehicles (i.e. those used on out of town journeys). For the urban deliveries the Karrier Cob/Scammell Mechanical horse became the norm from 1933.

Thanks to Bill Aldridge, author of many books on old commercials.