LMS Royal Scot Class

By 1926 the LMS urgently needed heavier express motive power for the West Coast main line. The post-Grouping LMS had inherited its express engines from the old LNWR (Compound 4-4-0s and Claughton 4-6-0s) and Midland Railway (Compounds), neither of which could handle the increasing weights of the principal Anglo-Scottish expresses. Sir Henry Fowler, the LMS's newly-appointed Chief Mechanical Engineer, was under acute time pressure, the company needed a new express engine in service quickly.

The Royal Scot was Fowler's answer. Working with the North British Locomotive Company of Glasgow (which contributed the production capacity that the LMS works could not), Fowler designed a three-cylinder 4-6-0 with 6 ft 9 in driving wheels, 18 × 26 in cylinders, and a 250 psi parallel boiler. The general arrangement borrowed from the Southern Railway's Lord Nelson Class (a contemporary three-cylinder 4-6-0). The first 50 engines were built by NBL in 1927 with the remaining 20 from Crewe, a remarkable production rate for the period.

The class entered service from July 1927. They were immediately a substantial improvement on what they replaced and worked the West Coast main-line top link through the late 1920s and 1930s. The principal long-term limitation was the parallel boiler, by the late 1930s, with the Black Fives and 8Fs showing the steaming and life-cycle benefits of the taper boiler, the case for rebuilding the Royal Scots became compelling.

The rebuild programme began in 1943 under H. G. Ivatt (the LMS's post-war CME) with engine 6103 as the first conversion. The rebuild was comprehensive, new Stanier-pattern domeless taper boiler, new cylinders with revised steam circuits, new smokebox, new running plate, new tender. By 1955 all 71 engines had been rebuilt. The rebuilds gave 30%+ improvement in fuel and water consumption, much higher route availability, and a working life of another 10–20 years.

The original Royal Scots were the LMS's heaviest express engines from 1927 to 1933 (when the Princess Royals took over the heaviest duties). They worked the Royal Scot, the Mid-Day Scot, the Royal Train, the Royal Highland, and the West Coast Postal. The 1933 American visit by 6100, coast-to-coast on the Baltimore & Ohio Railroad, gave the class international visibility and demonstrated British steam standards in North America.

The rebuild programme of 1943–1955 transformed the class. Post-rebuild the engines were measurably more economical and reliable than the originals, with route availability extended through 7P5F classification. The rebuilt Royal Scots were the principal LMR 7P engine after the Princess Coronations through the 1950s, working the West Coast main-line semi-fast and connecting expresses, the Trans-Pennine routes, and the Midland routes that could accommodate them.

British Railways inherited the original (mostly still-parallel-boilered) engines in 1948 and continued the rebuild programme through to 1955. From 1961 onwards the introduction of BR Type 4 diesels (Class 40 and Class 47) progressively displaced the class from front-line duties. The last Royal Scot in BR service was 46115 "Scots Guardsman", withdrawn from Carlisle Kingmoor in December 1965, by which point only the two preserved engines remained.

Two distinct outline phases. Original (1927–1942): a parallel-boilered three-cylinder 4-6-0 with Belpaire firebox, smoke deflectors fitted from 1929, and twin parallel boiler-rings. Rebuilt (1943–1955): Stanier-pattern domeless taper boiler (the same as the Black Five and 8F), double chimney from 1955, smoke deflectors, and a noticeably cleaner outline. The rebuild was so comprehensive, new boiler, new cylinders (with revised steam circuit), new smokebox, new running plate, that the rebuilt engines were effectively a new class sharing only the wheels, frame, and number with the originals. The class is named after British Army regiments, most names commemorate Scottish or northern English regiments, with brass nameplates carried beneath the boiler band.

6100 Royal Scot (later 46100), the class prototype, completed by the North British Locomotive Company in July 1927 (the first of fifty engines built by NBL, Crewe built only twenty in this batch). Visited the United States in 1933, hauling specials on the Baltimore & Ohio Railroad including a coast-to-coast Canadian-Pacific tour. Rebuilt 1950 to Stanier taper boiler form. Withdrawn from BR October 1962 and privately preserved. Currently main-line registered with the 6100 Royal Scot Locomotive and General Trust, based at Crewe.

6115 Scots Guardsman (later 46115), completed at Crewe in October 1927. Rebuilt 1947 to Stanier taper boiler. The very last Royal Scot in BR service, withdrawn from Carlisle Kingmoor in December 1965. Privately preserved and currently main-line registered with the West Coast Railway Company at Carnforth.

6170 British Legion (later 46170), the class's most experimental member. Originally built 1929 as the unique Fury, with a Schmidt-Henschel high-pressure water-tube boiler at 1,400 psi (the highest pressure ever fitted to a British steam locomotive). The boiler was technically successful but commercially impractical, the engine made few revenue trips before its boiler failed in 1930, killing the test driver. Rebuilt 1935 as a conventional Royal Scot with the Stanier taper boiler (effectively a prototype rebuild, the trial run for the rebuild programme that began in earnest from 1943). Renamed British Legion. Withdrawn from BR December 1962 and broken up.

LMS era (1927–1947): the class was allocated principally to Camden (London Euston), Crewe North, Edge Hill (Liverpool), Polmadie (Glasgow), and Holbeck (Leeds). Camden's 1A link was the principal Royal Scot allocation, working the Royal Scot, the Mid-Day Scot, and the Royal Train.

British Railways London Midland Region (1948–1965): after rebuilding, the class was redistributed across the LMR, Camden, Crewe North, Edge Hill, Holbeck, Polmadie, Saltley (Birmingham), and Annesley. The rebuilt Royal Scots became reliable mainstays of the LMR's 7P link.

Final years (1962–1965): displacement by the introduction of BR Type 4 diesels from 1961 saw the class progressively withdrawn through the early-to-mid 1960s. The last Royal Scot in service was 46115 "Scots Guardsman", withdrawn from Carlisle Kingmoor in December 1965.

LMS lined crimson lake (1927–1942): the original engines were outshopped in LMS lined crimson lake with gold lining and serif "L M S" lettering, the LMS standard express livery from 1928 onwards.

LMS unlined black (1939–1947): wartime conditions saw most of the class temporarily painted in plain black with shaded lettering. Some engines began returning to crimson lake in late LMS days but most were still in black at nationalisation.

British Railways experimental blue (1948–1949): some examples briefly carried BR experimental dark blue, before standardising on Brunswick green from 1949.

British Railways Brunswick green (1949–1965): from 1949 the class wore BR-standard lined Brunswick green with the early lion-and-wheel emblem (later the late BR crest from 1956). This was the dominant livery on the rebuilds, the rebuild programme rolled engines into BR Brunswick green as part of the rebuild process. Most rebuilds spent their entire post-rebuild lives in BR Brunswick green.