By 1945, Edward Thompson was in charge of engineering on the LNER and post-war he designed a new range of coaches which bore no resemblance to those of his predecessor. Thompson stock was longer, on 61.5ft underframes, and built in steel on wooden frames.

The internal layout was also completely different, having the entrance vestibules not at the ends but between groups of compartments. Arriving passengers needed to pass only one compartment in taking up their seats. An embellishment by which they are also recognised is the oval lavatory window. The main windows, without ventilators, looked large and stark, with their sharp corners. These were softened with rounder corners by Peppercorn when he took over from Thompson on the latter's retirement.