It might be worth remembering that these trains were not exclusively made up of tankers.. They frequently featured any of the various southern utility vans, specially-built milk vans (in the early days), GWR slat-sided vehicles etc.. - most of which would be carrying milk &/or cream in churns. There were also fitted flat wagons carrying road tankers, depending on the source of the traffic, as not all the dairies had direct rail access..