GWR 5101 Class
5164 at Totnes in 1958
Type and origin Power type Steam Designer Charles Collett Builder GWR Swindon Works Order number Lots 257, 259, 284, 292, 313, 323, 335, 361, 369 Build date 1929–1949 Total produced 140
Specifications Configuration: ​  • Whyte 2-6-2T  • UIC 1′C1′ h2t Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 2 in (0.965 m) Driver dia. 5 ft 8 in (1.727 m) Trailing dia. 3 ft 8 in (1.118 m) Length 41 ft (12.50 m) Loco weight 78.45 long tons (79.71 t; 87.86 short tons) Fuel type Coal Fuel capacity 4 long tons (4.1 t; 4.5 short tons) Water cap. 2,000 imp gal (9,100 L; 2,400 US gal) Firebox: ​  • Grate area 20.35 sq ft (1.891 m2) Boiler GWR Number 2 Boiler pressure 200 psi (1,400 kPa) Heating surface: ​  • Firebox 121.8 sq ft (11.32 m2)  • Tubes and flues 1,144.94 sq ft (106.368 m2) Superheater: ​  • Heating area 82.2 sq ft (7.64 m2) Cylinders Two Cylinder size 18 in × 30 in (457 mm × 762 mm)
Performance figures Tractive effort 24,300 lbf (108 kN)
Career Operators Great Western Railway British Railways Class GWR 5101 Power class GWR D BR 4MT Numbers 5101–5199, 4100–4179 Axle load class GWR Blue Locale Western Region Withdrawn April 1956 – November 1965 Disposition 8 preserved, 1 used for spares, 1 rebuilt into tender engine; remainder scrapped

The GWR 5101 Class or 'Large Prairie' is a class of 2-6-2T steam locomotives of the Great Western Railway.

The 5101 Class were medium-sized tank engines used for suburban and local passenger services all over the Great Western Railway system. The class was an updated version, by Collett, of Churchward's 1903 3100/5100 Class.

The original 40 members of the 3100 class were renumbered 5100 and 5111 to 5149 in 1927. The first batches of 5101s filled in the numbers 5101 to 5110 and extended the class from 5150 to 5189. They were little changed from the Churchward locomotives as they then were, but had an increased axle loading of 17 long tons 12 cwt (39,400 lb or 17.9 t); the maximum permitted for the ‘Blue’ route availability. Bunkers were of the standard Collett design with greater coal capacity. The 5100 number series was exhausted in 1934, and further new locomotives were numbered from 4100. The last 20 were built after nationalisation.^[1]

As both freight and passenger traffic on branch lines declined post-World War II with increasing volumes of private motor cars, and replacement on urban services by diesel-powered rail cars, the bulk of the class found itself allocated to various mainline support duties, mainly banking and piloting, often on the South Devon Banks on the Exeter to Plymouth Line, or around the Severn Tunnel on the South Wales Main Line.

A number of the class - 4110, 4115, 4121, 4144, 4150, 4156 and 4160 - ended their operational lives allocated to the major locomotive shed (88E) at Severn Tunnel Junction, undertaking piloting and banking duties through both the Severn Tunnel and the associated goods yard.^[3] Assistance was needed by all heavy trains through the Severn Tunnel, which entailed: 3.5 miles (5.6 km) of 1-in-90 down to the middle of the tunnel; then a further 3.5 miles (5.6 km) at 1-in-100 up to Pilning; a short level then 3.5 miles (5.6 km) more at 1-in-100 to Patchway. However, the pilot locomotive usually came off at Pilning. Several of this group were sold for scrap to Woodham Brothers and consequently have survived into preservation.

• On 30 November 1948, locomotive 4150 was running round its train at Lapworth when it was in collision with a passenger train hauled by 5022 Wigmore Castle, which had overrun signals.^[4] Eight passengers were injured.^[5]

The below list shows when all of the original 5101's and later 4100's were withdrawn from service.

Ten of the class were preserved after withdrawal in the 1960s (six built in the 1930s before World War II and four built after the war in the late 1940s, one of which under the British Railways banner). As of 2023, six have run in preservation, one is under restoration, one is still in scrapyard condition, one has acted as a donor locomotive for other projects, and one has been rebuilt into a tender engine:

Number	Built	Withdrawn	Service Life	Owner	Current Location	Status	Livery	Notes	Image
5164	Nov 1930	Apr 1963	32 Years, 5 months	Erlestoke Manor Fund	Tyseley Locomotive Works	Stored	GWR Unlined Green, Great Western Lettering	Normally located at the Severn Valley Railway but on static display at Barrow Hill MPD since 2014 following expiry of boiler certificate on 5 January 2014. Ownership transferred to the Erlestoke Manor Fund in 2021; as of January 2022 plans to overhaul the locomotive are underway.[6] The engine was moved from Barrow Hill Engine Shed to Tyseley Locomotive Works for assessment in November 2023.[7]
5193	Oct 1934	Jun 1962	27 Years, 8 months	West Somerset Railway plc	West Somerset Railway	Operational (Donor locomotive)	BR Lined Green, Early Emblem	Originally built in 1934, withdrawn in 1962 and recovered from Woodham Brothers scrapyard in 1979. Rebuilt by the West Somerset Railway into a 2-6-0 resembling a small boilered version of the GWR 4300 Class, which has been numbered 9351. Returned to service in 2019 following an overhaul.
5199	Nov 1934	Mar 1963	28 Years, 3 months	5199 Project	West Somerset Railway	Operational	GWR Unlined Green, Great Western Lettering	Overhaul completed 23 November 2014. Repainted into GWR Green livery in 2021.[8]
4110	Oct 1936	Jun 1965	28 Years, 8 months	Dartmouth Steam Railway	East Somerset Railway	Operational	BR Unlined Green, Late Crest	Sold in May 2015 by GWR Preservation Group Limited of Southall Railway Centre to WSR plc. Sold again in January 2019 to the Paignton and Dartmouth Steam Railway. It was sent to the East Somerset Railway in January 2020. Returned to steam in 2023
4115	Oct 1936	Jun 1965	28 Years, 8 months	Great Western Society	Didcot Railway Centre	Donor locomotive, frames scrapped in 2016.[9]		Built October 1936, withdrawn from service in June 1965. One of the "Barry Ten", she was sold to the Great Western Society, Didcot in 2010, to act as a donor locomotive. Its frames were scrapped in 2016:[10]
4121	Dec 1937	Jun 1965	27 Years, 6 months		Tyseley Locomotive Works	Unrestored, partially stripped	N/A	Stored at Tyseley[as of?] in a partially stripped down state
4141	Aug 1946	Mar 1963	16 Years, 7 months	Roger Wright	Epping Ongar Railway	Awaiting completion of repairs	BR Lined Green, Late Crest	Returned to steam in 2012 after an overhaul, but currently out of service awaiting boiler repairs.
4144	Sept 1946	Jun 1965	18 Years, 8 months	Great Western Society	Didcot Railway Centre	Operational	GWR Unlined Green, GWR Lettering	Returned to steam in 2015 after an overhaul. Loaned to the Kent & East Sussex Railway for the 2020 season. Returned to Didcot Railway Centre before visiting other railways. At the Kent & East Sussex Railway for the Santa’s in 2021. Operational at the Chinnor and Princes Risborough Railway as of the summer of 2023.
4150	Jun 1947	Jun 1965	17 Years, 11 months	4150 Fund	Severn Valley Railway	Restoration in progress[as of?]	N/A
4160	Sept 1948	Jun 1965	16 Years, 8 months	4160 Ltd	South Devon Railway	Under Overhaul	N/A	Overhauled in 2007, previously operated on the West Somerset Railway. Sent to the Llangollen Railway in January 2016 for overhaul. Moved to the South Devon Railway for the completion of its overhaul, upon which it shall become a resident of the line under the custodianship of 5542 Ltd.[11]

Graham Farish manufacture a model of the Large Prairie in N scale.^{[when?][citation needed]} Hornby have manufactured two models of the class in 00 gauge in both Great Western and British railway liveries; the first was based on a 1980's Airfix model of the engine, the second was a 2020 re-tooled model with a 5 pole motor.^{[citation needed]} Dapol have a 00 gauge model due for release in q4 2021; this has both GWR and BR livery versions planned. Heljan are planning on producing a model of the large prairie in O gauge in 2017.^[12] Sonic Models have announced they producing an N scale model, due for release in April/May.^{[year needed][13]}

• GWR 3100/5100 Class (1906)
• GWR 3150 Class
• GWR 6100 Class
• GWR 3100 Class (1938)
• GWR 8100 Class
• List of GWR standard classes with two outside cylinders

• Allcock, N. J.; Davies, F. K.; le Fleming, H. M.; Maskelyne, J. N.; Reed, P. J. T.; Tabor, F. J. (1968) [1951]. White, D. E. (ed.). The Locomotives of the Great Western Railway, part one: Preliminary Survey. Kenilworth: RCTS.

• 5101 tank class
• 4144 - 2-6-2T
• The 4150 Fund
• The 5164 Website Archived 3 March 2016 at the Wayback Machine
• 4160 History