Charles B. Collett developed a new range of standard coaches from 1922 to coincide with the reintroduction of the chocolate and cream livery onto the company’s network. These covered a wide variety of types, but the most common type introduced between 1925 and 1929 was the ‘bow-ended’ corridor coach, of which several hundred were built at Swindon. 
The idea of the ‘bow ends’ was to reduce the length of the corridor connections between carriages following complaints from nervous passengers about walking across them when the train was travelling at speed. They went on to form the backbone of main line sets for 20 years.