GWR railcars

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GWR diesel railcars were introduced between 1934 and 1942 to replace steam locomotives and carriages. A total of 38 cars were built (Nos. 1–38) by Park Royal, Gloucester RCW, and Swindon Works. They entered service from 1934 and remained in use into the 1960s. Five cars were destroyed by fires, and three survive in preservation today. Their successors were the British Rail Class 121 and 122.

What they were like
- The early cars had rounded “flying banana” bodies; later, more angular designs like No. 27 were common.
- Capacity varied from 44 to 70 seats, with later arrangements able to add a corridor coach to reach around 184 seats.
- They ran on standard gauge (4 ft 8½ in) and could reach speeds from about 63 to 80 mph.
- Heating initially used waste heat from the engine; later cars used steam heating via a Vapor Clarkson generator to heat the car and any attached trailers.

Engines and drive
- Nos. 1–18 used AEC diesel engines delivering up to 130 hp. Nos. 19–38 used a modified engine with 105 hp.
- Some early units had two engines. The cars used an unusual external Cardan shaft drive, with later units adopting dual-drive arrangements.
- Nos. 2–4 had a unique vacuum-hydraulic braking system.

Service history
- Prototype No. 1 first ran on 1 December 1933 (Paddington to Reading); public service followed on the Slough–Windsor–Didcot route.
- The first long-distance service was Birmingham Snow Hill to Cardiff General in 2 hours 20 minutes (1934), carrying 44 seats.
- Nos. 5–7 entered service in 1935 with 70 seats (London–Oxford–Hereford). The later batches (Nos. 8–34) ran through 1936–1941, including some express parcels units. Nos. 35–38, introduced in 1941, were twin-coupled sets with driving cabs at both ends and could be expanded to carry more passengers.

Preservation and models
- Five cars were lost to fires; three have been preserved.
- There are several model versions available from Hornby, Dapol, Heljan, and Graham Farish.