British Railways placed the order with BUT in summer 56 for the equipment required for the 98 power cars and 47 trailers of the first batch. The order, along with equipment ordered by Cravens for 66 power cars and the three parcels cars, was valued at £830,000.
The first batch was ordered for the WR's West Country dieselisation scheme, which it hoped to complete by the end of 1959. The sets were expected to work between Bristol & South Devon.
In February 1959 the BTC place an order with BUT for the equipment for the seven ScR sets, along with equipment for Class 108s and 127s being built at Derby.