The Westerns were the last survivors of the short lived hydraulic designs and 74 were constructed at Swindon and Crewe between 1961 & 1963. Entirely based on the former GWR mainline, the twin Maybach engined machines worked the WR's premier passenger trains but were equally at home on heavy freight. BR's decision to standardise to diesel-electric traction meant the final class member was overhauled in 1973, but they continued longer than expected with the last examples withdrawn from traffic in February 1977.