In 1937, Maunsell's replacement Oliver Bulleid saw no need to improve draughting of the class, and spared them from trials with Lemaître multiple-jet blastpipes and wide-diameter chimneys. However, he had Maunsell's smokebox-mounted anti-vacuum snifting valves removed at the end of the Second World War in an effort to reduce maintenance. Bulleid also had eight new tenders built specially for the left-hand drive locomotives. In 1947, No. 1831 was given electric lighting and converted to oil-burning as part of government-backed fuel trials in anticipation of a post-war coal shortage, though it was reverted to coal-firing in December 1948.