This design with its characteristic sloping sides evolved from pre 1939 private owner wagons built by Chas. Roberts and Coy. The Government chose it for further construction during the subsequent hostilities. To meet a shortage of rolling stock in France after Liberation, over 2,500 were shipped there. Of these around 1,900 were returned to BR in the early 1950s. (The balance had an honourable career in France as ballast wagons.) By this time BR had a fleet of around 10,000 of these wagons of which about 2,300 were ex private owner wagons. Withdrawal took place in the middle 1960s although many were sold to industry as "internal users" Transfers for 1950s and 1960s periods included.