Class 50 Refurbished

The second English Electric type 4 design concept featured the uprated 16CSVT engine in a Deltic type bodyshell identified as DP2. This single 2,700bhp engined locomotive proved to be equal to the 3,300bhp twin-engined Deltics on all but the most arduous of their duties. While the BRCW prototypes' Sulzer engine allied to Brush electrical machinery was chosen for BRs standard type 4 locomotive (class 47) DP2 had impressed. The West Coast Mainline electrification scheme from London to Liverpool and Manchester had been commissioned in 1965, reducing journey times on the southern end of the route. However north of Crewe services were still hauled by early diesel locomotives. To provide a quick upgrade in speed over the hills to Scotland BR arranged to lease 50 of 2,700bhp locomotives from English Electric for 10 years.
Unlike the bulldog-nosed Deltic bodyshell of DP2 the production locomotives featured the standard BR design flat two-window cab ends and the 50 locomotives entered service in 1967/8, numbered D400 to D449. Unlike the 47s the entire class was fitted for multiple working, it being the intent to operate them in pairs, the installed 5,400bhp delivering a performance similar to the rated power of the new (class 86) electric locomotives.

The West Coast electrification reached Glasgow in 1974, releasing these diesel locomotives from their original duties. At the same time the Western diesel hydraulic fleet was being phased out and the 'D400s' were sent south to replace the 'Western' class on London Paddington to Bristol, South Wales and the South West expresses.
The Western region had become accustomed to working their diesel locomotives hard and the D400s were not welcomed. Not only were these locomotives replacing the much loved 'thousands' but they were not in the best condition and the Westerns were proving more reliable!

By 1979 BR had decided to purchase the leased locomotives and action was required to address the class' issues, including over-complex control systems like slow speed control which had been specified by BR but was never likely to be used on express passenger duties!
A comprehensive refurbishment programme was designed at Doncaster works which included the removal of the original inertial air filtration system which drew air in with a vacuuming noise, but quickly clogged in damp conditions, dynamic brakes, ventilation for which was in the 'cut out' roof section and simplification of the control circuitry (eg SSC removal). Improvements included better segregation of the engine and main generator, allowing clean air to be supplied to the generator compartment, keeping engine oil out, a through overhaul of all the electrical machinery, improving insulation, plating over of redundant roof and headcode apertures and the addition of high-intensity headlights.
The first refurbished locomotives returned to service in standard rail blue livery (and initially with the new headlight aperture covered over as the headlights hadn't arrived!) but from 1980 the revised 'large logo' blue livery with wrap-around yellow ends was applied.