LNER Class P1

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LNER Class P1
LNER mikado 2-8-2, 2394 (CJ Allen, Steel Highway, 1928).jpg
No. 2394, circa. 1928, with booster engine and Westinghouse pump
Type and origin
Power type steam
Designer Sir Nigel Gresley
Builder London & North Eastern Railway
Build date June & November 1925
Total produced 2
Configuration 2-8-2
Gauge 1,435 mm (4 ft 8 12 in)
Leading wheel
3 ft 2 in (0.97 m)
Driver diameter 5 ft 2 in (1.57 m)
Trailing wheel
3 ft 8 in (1.12 m)
Wheelbase 36 ft 2 in (11.02 m)
Axle load 18.65 long tons (18.95 t)
Locomotive weight 100 long tons (101.60 t)
Tender weight 51.4 long tons (52.2 t)
Locomotive and tender
combined weight
151.4 long tons (153.8 t)
Boiler 6 ft 5 in (1.96 m) max.
Boiler pressure 180 psi (1.2 MPa)
Firegrate area 41.25 sq ft (3.832 m2)
Heating surface:
– Tubes
1,880 sq ft (175 m2)
– Flues 835 sq ft (77.6 m2)
– Firebox 215 sq ft (20.0 m2)
– Total 3,455 sq ft (321.0 m2)
Superheater type Robinson
Cylinders 3, with 2 more in a booster unit
Cylinder size 20 in × 26 in (510 mm × 660 mm)
10 in × 12 in (250 mm × 300 mm) booster
Valve gear Walschaerts & Gresley, with steam reversing gear
Performance figures
Tractive effort (85% boiler pressure) 38,500 lbf (171 kN)
8,500 lbf (38 kN) booster

The London and North Eastern Railway Class P1 Mineral 2-8-2 Mikado was a class of two steam locomotives designed by Nigel Gresley. They were two of the most powerful freight locomotives ever designed for a British railway. It was initially intended they be a more powerful 2-10-0 version of the earlier Class O2 2-8-0s. The design was submitted in August 1923, for use between Peterborough and London, and also between Immingham and Wath marshalling yard. The power was quoted as being 25% more than the O2.

Construction and into service[edit]

The first P1, No 2393, was completed by Doncaster in June 1925 and was shown at the Darlington Centenary celebrations in July, with its sister No 2394 following in November 1925. Both were externally rather similar, although 2393 had a 32-element superheater while 2394 had a larger 62-element 'E' type superheater.[1] They were the first 2-8-2 locomotives to be built in Britain for local use, although not the first designed. Both were allocated to New England shed after completion where they were subjected to regular testing.

In service, the P1s could handle 100-wagon coal trains, although these were an operational hazard due to their overhanging track circuits and being too long for many of the passing loops. They were also coal-hungry engines, with a 1926 Locomotive Inspectors Conference Report stating that the engines used 131 lb of coal per mile.[2] However, they were still thought of highly enough in 1926 that it was proposed to build another four P1s to replace an equivalent number of 0-8-0s.

The boosters[edit]

The P1 class engines were initially equipped with two-cylinder boosters attached to the trailing axle. These were engaged using a Westinghouse pump mounted on the boiler to engage the cylinder clutch.[3] These had a tractive effort of 8,500 lb when used, increasing the tractive effort of the locomotive from 38,500 lb to 47,000 lb. It was intended by Gresley these boosters would be used to assist the locomotive while starting and topping the banks over which they travelled.

The tenders equipped to the P1s had a specially-designed dragbox to accommodate this equipment. In practice, the boosters were troublesome; using them would fill the cab with steam, while the fireman's workload would be doubled. The steam pipes from the boiler to the booster were prone to fracture, particularly on the sharp curves of the turning triangle at New England shed. The boosters were removed from engines 2393 and 2394 in 1938 and 1937 respectively.[4]

Service and withdrawal[edit]

The two P1s were only ever used between New England and Ferme Park, the only route deemed suitable for them by the Operating Department. They were however largely uneconomic as they were hauling trains of less than 1000 tons, for which they were built for. In 1934, No 2394 was experimentally tried on the 07.45am semi-fast from New England to Kings Cross as part of the planning stage for P2 class locomotive 2001 Cock o' the North. Although the engine was able to reach a maximum speed of 65 mph, this put too much stress on the fireman who later commented that he was thankful not to have been going beyond Peterborough.[5]

In 1942, both engines were overhauled and their original boilers, then in very poor condition, were replaced with A3-type 220 lb boilers and their cylinder diameter was reduced to 19 inches, leading to an increased tractive effort of 42,500 lb. The valve motion was retained in its original short-lap travel configuration. This rebuilding, which took place in November and January 1942 for engines 2393 and 2394 respectively, saw them reclassified as Class P1/2.

Due to the reduction of heavy freight trains after the Second World War, both engines were withdrawn by Edward Thompson and scrapped in July 1945, the first Gresley locomotives to be withdrawn and scrapped by intention. The six-wheeled tenders were modified with standard dragboxes to run behind new Thompson Class B2 4-6-0s Nos 2815 and 1632, while the boilers were removed and fitted to Gresley A1s No 2557 Blair Atholl and 2565 Merry Hampton during their conversion from Class A1 to Class A3.


  1. ^ Cliffe, J; Clay, J. F (1973). The LNER's 2-6-2 and 2-8-2 Classes. Ian Allan. p. 25. 
  2. ^ Cliffe & Clay 1973, p. 26
  3. ^ Cliffe & Clay 1973, p. 24
  4. ^ http://www.lner.info/locos/P/p1.shtml
  5. ^ Cliffe & Clay 1973, p. 27