Well well - Northern Dairies was a very big company local to where I live in Hull (although they moved to Leeds when the council knocked down their building - one of the tallest in Hull - to build a new shopping centre..)
We all had their milk delivered, but I never knew they actually designed and built any vehicles (and my uncle was a senior manager there before they moved him to be the Area Manager for the North East, in Middlesbrough..)
The vehicle in the B&W photo has a Hull registration dating from about 1950 or 1951.