This locomotive demonstrated significant advances in performance and efficiency compared to standard SAR steam practice, but the work came at a time when the phasing out of steam traction had already reached an advanced stage, and was too late to stop it continuing. Wardale therefore left the SAR to join the American Coal Enterprises' (ACE) team in the USA in 1984, charged with developing classical Stephensonian steam traction for export to developing railways. Unfortunately ACE failed to secure its start-up capital, but in 1985 Wardale was part of a small delegation from the UK invited to China by the Chinese National Railways to discuss improving its QJ Class heavy freight 2-10-2's, which were then still being manufactured. As a result of this he became the Technical Consultant to the Datong Locomotive Factory in 1986, and produced the full design for the necessary modifications to this class. However this work also came too late, for during the course of the 3-year contract at Datong the Chinese Railways' policy changed from one of continued reliance on steam traction to one of phasing it out as quickly as possible. Although the design work was completed it was therefore not possible to put it into practice, practical work being limited to a certain amount of component testing.
Wardale left Datong in 1989 and has since, amongst other pursuits, written a critically acclaimed book, The Red Devil and Other Tales from the Age of Steam, describing his work on steam locomotives in South Africa, America and China.
David completed the Fundamental Design Calculations for the 5AT in 2005 and continues to support the project with technical advice. He now lives in semi-retirement in Scotland.