In 1936 Collett introduced a considerable change in Great Western coaching stock. The new style was flat ended and mounted on 60′ and 61′ underframes. They featured end vestibules and sliding ventilators integral with the windows on the compartment side. The corridor side had deep picture windows without vents but separated by equally deep droplights. The windows reached from a low waistline almost to the cantrail, hence they became known as large windowed stock.
Later coaches such as the ‘Sunshine Stock’ and Hawksworths echoed many of the features introduced by this large windowed design.