All five locomotives were withdrawn on 30 December 1967. By this time they were non-standard, even for hydraulic designs, although according to Laira staff reliability was not a problem as many have thought. BR had been ordered to reduce the number of main line locomotive classes from 28 to 15 by 1974, primarily by eliminating types which were known to be unreliable, had high maintenance costs or were so few in number as to be non-standard. As the table below shows, there was a substantial gap between delivery of D601 and D602 because NBL had to equip itself to construct the engines and transmissions for these three locomotives. By this time the first Swindon-built D800s had entered service and these were the lightweight and more powerful diesel-hydraulic locomotives that the WR really wanted.