This carriage was actually built by British Railways, but to the last series of designs developed by the LMS before the railways were nationalised. The diagram dates from 1947, and would probably have been the basis for on-going LMS construction if Nationalisation had not intervened in 1948. The side panels are steel, supported on a steel bodyframe. While this diagram is clearly out of the Stanier stable, it is also the first prototype of the British Railways Mark 1 body.