Worcester had been home to many of the former Great Western Railcars since before the Second World War, but this apart the diesels were relatively slow to threaten the domination of the steam locomotive.
First serious inroads into the domination of the steam locomotive came when Birmingham based suburban diesel multiple units arrived in 1957.
These were followed almost immediately by dieselisation of the Cardiff and Hereford to Birmingham Snow Hill passenger services with Swindon 3-car 'cross country' diesel multiple units which arrived from 1958.
Five 165hp diesel electric shunting locomotives were purchased from Ruston & Hornsby of Lincoln for British Railways for use at various Permanent Way Depots. One such depot was at Newland, near Malvern. The first of the five locomotives in the class No.PWM650 arrived at Newland about 5th May 1958 and was serviced and fuelled at Worcester.
Three 204hp diesel mechanical shunting locomotives were allocated to Worcester during 1960. The first of these locomotives was No.D2139 which was transferred from Gloucester (Horton Road) shed.
Bristol (Bath Road) depot received an allocation of ten Sulzer 'Peak' class diesel locomotives (Nos.33 to 42) from new in August 1961 and these were soon regularly seen at Worcester on inter-regional services to Derby and the north-east of England. They were soon joined by Midland Region based examples of the same class.
However, through all of these changes the London (Paddington) to Worcester and Hereford express passenger trains remained in the hands of steam locomotives from the era of the Great Western Railway, primarily 4-6-0s of the 'Castle' and 'Hall' classes, allocated to Worcester and Old Oak Common (London) sheds.
The first main line diesels to operate from Worcester locomotive sheds were Birmingham RCW type 3 diesels (later Class 33) from the Southern Region. These arrived during the severe winter of January 1963. The first such example was No.D6518 (a photograph of which taken by Richard Moreton appears in the March 1963 issue of 'Modern Railways' with Saltley's Stanier Black 5 No.44963 at Worcester Foregate Street station on 21st January 1963 on the 10:05 from Hereford to Paddington). This was replaced by others of the same type during January and February 1963. For instance, Gerald Wadley records No.D6536 at Malvern Link on 21st February 1963.
The type 3's were not equipped with steam heating apparatus and were not intended to replace steam locomotives on the express passenger services to London but were based at Worcester for crew training prior to dieselisation of the Bitumen trains from Fawley to Bromford Bridge.
The writing was nevertheless on the wall for steam and came later in 1963 in the shape of Beyer Peacock 'Hymek' type 3 (later class 35) locomotives. 101 of this type of locomotive were built at Gorton, Manchester. The first to arrive at Worcester for crew training duties, as confirmed by Gerald Wadley's notebooks was No.D7076 of Cardiff Canton shed. Gerald first recorded this locomotive at Malvern Link on 13th May 1963. Other of the same class were recorded later that same week.
The 'Hymek' diesel locomotives took over about half of the Paddington express services during the Summer 1963 timetable but were still working to steam locomotive schedules. The premier train on the line was known as 'The Cathedrals Express'.
With much ado British Railways heralded the end of steam working of passenger trains from Worcester to Paddington with a full press turn-out and sparkling 'Castle' class 4-6-0 No.7023 'Penrice Castle' (of Worcester shed) on the last Saturday of operation of the Summer 1963 timetable on the 11:10 to London on 7th September 1963. 'Penrice Castle' was immediately retired to store outside the back of Worcester shed and that should have been just about been it for high speed main line steam at Worcester.
However, things did not go to plan, as perhaps due to lack of adequate servicing facilities at Worcester the 'Hymeks' failed on an almost daily basis. This was followed by major problems with the 'Western' class diesel locomotives that led to more steam substitutions as 'Hymek' diesels were moved to Cardiff. The Worcester Locomotive Society house magazine 'Big Four' reported that by 30th October 1963 steam locomotives were working all express passenger services from Worcester to London.
By Christmas 1963, the situation had become so desperate that 'Penrice Castle' was brought back into traffic (still looking immaculate) but more alarmingly a tranche of worn out 'Castles' were drafted in from far and wide. Decrepit examples were even allocated to Hereford shed, a depot that had never before seen an allocation of 'Castles'.
The first class 08 shunter to arrive at Worcester was No.D4118 in 1964.
Diesels slowly returned to Worcester but by April 1964 they had again virtually disappeared from the London service as the 'Hymeks' were sent elsewhere to cover for more defective 'Western' class diesel locomotives.
The diesels situation had improved by June 1964 such that it was possible to release half of Worcester's 'Castles' including some of the best engines, Nos.7011 'Banbury Castle' and No.7023 'Penrice Castle', to the Oxley and Tyseley sheds in the West Midlands.
Worcester favourite No.5054 'Earl of Ducie' was used on a number of railtours in July 1964 but with no scheduled London express duties from the Summer 1964 timetable, there was little work for the four remaining 'Castles' at Worcester but they hung on with more mundane duties such as engineering and stopping trains. No.5054 (together with No.7022 'Hereford Castle') was released to Gloucester shed in September 1964 but No.5054 was promptly withdrawn and dumped at Worcester shed.
Dieselisation of the banking duties on the Lickey Incline commenced in July 1964 will the arrival of English Electric built 1,750hp diesel locomotive No.D6938 which was soon followed by others of the same class.
During July 1964 Brush type 4 diesel electric locomotive No.D1749 arrived at Worcester for crew training duties and later was replaced by blue 'XP64' liveried example No.D1733.
With the end of the Summer 1964 timetable the last 'Castles' at Worcester (No.7005 'Sir Edward Elgar' and No.7025 'Sudeley Castle') were withdrawn leaving only the small stud at Gloucester and in the West Midlands depots to survive into 1965. A correspondent to 'The Railway Observer' noted Nos.5054, 7005, 7025 and 5000 dumped on Worcester shed on 6th October 1964.
Worcester's locomotive works continued to repair and overhaul steam locomotives including No.6435 that was restored to GWR livery for a private owner. It is seen awaiting overhaul on 31st December 1964.