Seventy 4-6-4 type R-class express mainline passenger engines entered service in 1951-2 allowing many of the older A2-class engines to be retired, while sixty 2-8-0 type J-class engines designed to supplement the K & N-class engines on general branchline duties were introduced in 1953-54.

Sadly, due to the early success of diesel locomotives in reducing running costs, many of these fine locomotives were withdrawn without ever undergoing a major overhaul and after completing little more than 200,000 kilometres service, less than a tenth of a steam engine's normal life expectancy.