In the end the diesel-hydraulic experiment foundered on low fleet numbers, poor maintenance conditions and design issues; not on its German heritage or development of a novel configuration.

BR's Swindon Works maintained all the diesel-hydraulic locomotives, and their early demise resulted in a much reduced workload and hastened its eventual closure in 1986.

The most serious continual problem with the class was a mismatch between the Maybach MD655 engines and the Voith L630rV three speed hydraulic transmissions, a design fault.

This factor, the South Devon Banks (a major part of their running grounds) and the deleterious effect on worn-out engines, all contributed against the Westerns continuing in top-line service.

Its non-standard design added to its maintenance costs at a time when national British Rail policy was moving away from diesel-hydraulics.

In 1968–69, the Westerns received train air brake equipment in addition to their vacuum exhausters, thus significantly extending their working lives, unlike the similar but lower-powered, Warship class.

[6] However, as with the Warships, it proved impossible to equip them with electric train heating (ETH, or head-end power in US terminology).

[7] The highest recorded speed with a Western that O. S. Nock was aware of was 102 mph (164 km/h) when D1068 hauled nine coaches (305 tons gross) down 1 in 1,320 (i.e. virtually level) at Southall.

The train averaged exactly 100 mph (161 km/h) for 12.8 miles (20.6 km) between Slough and Ealing whilst hauling a service from Reading to Paddington.

The highest output that came to my notice was a sustained 85 mph (137 km/h) hauling 560 tons descending 1 in 1,320, which equates to 1,500 edhp (equivalent drawbar horsepower)".

[9] A similar result was obtained when Clough & Beckett[10] compared the performance of type 4 diesel locomotives (Classes 45/46/47/50/52) hauling trains up the ascent to Whiteball summit.

As withdrawal was already planned when the scheme was introduced and because of the cast number plates, it was not considered cost effective to renumber the locomotives.

On many Westerns, the headcode was set to display the locomotive's number in contravention of this directive and most surviving members of the class ran like this until they were scrapped.

[20] When the initial batch of Westerns was being built in 1961–2, British Rail was considering a new unified corporate colour scheme but had not yet made a final decision on what it would be.

[14] Remaining deliveries carried the all-over maroon livery, initially without yellow warning panels, but the latter were applied from new after D1010 of the Swindon-built, and D1043 of the Crewe-built locomotives.

The locomotive is not believed to have run in this condition, but was released to traffic in the golden ochre livery with standard small yellow panels.

Some early photographs of the blue livery give it a more metallic shade which is even more evident on the locomotives with small yellow panels.

D1022 Western Sentinel was a candidate for preservation and was planned to be purchased by the DTG (Diesel Traction Group), but it was scrapped.