By 1923, the year in which almost all the railways in Great Britain were grouped into four national companies, 282 million gallons of milk were being transported annually by rail.
[1] Of this traffic the Great Western Railway, serving the rural and highly agricultural West of England and South Wales, had the largest share.
It was followed by the LMS, which collected from Cumbria and North Wales; the Southern, deriving the bulk of its traffic from the Somerset and Dorset Railway; and finally the LNER, which served East Anglia.
This resulted in the need to pull the heavy milk train with a high-powered express locomotive, in order to keep time delays to a minimum.
The Cornish train would pick up at: Lostwithiel; Totnes for Ashburton; Exeter for both Hemyock and Torrington; then direct via Tiverton Junction to Kensington.
Although both trains were only scheduled to travel once a day in either direction, the 70,000,000 imperial gallons (320,000,000 L; 84,000,000 US gal) that they shipped annually still represented 25% of the UK's total milk shipment.
Using refurbished two- and three-axle wagons, the MMB had newly manufactured 5-foot-6-inch (1.68 m) diameter aluminium milk tanks chain-anchored to the chassis.
[1] After the contract was cancelled, the MMB kept the refurbished milk tank wagons in store on their own premises to overcome any difficulties in road transport, before disposing of the entire fleet five years later.