They were an enlarged and improved version of his previous design, the LMS Princess Royal Class, and on test were some of the most powerful steam locomotives ever used in Britain at 2,511 dbhp.

Although the prior introduction of the Princess Royal class had provided the London Midland and Scottish Railway (LMS) with more powerful locomotives to be used on the main line between London Euston and Glasgow Central, the board of directors were persuaded in 1936 that more such locomotives would be needed, particularly as they were being asked to approve the introduction of a new non-stop service between those cities, designated the Coronation Scot.

[8]: 73 [11] After introduction it was subsequently found that its aerodynamic form failed to disturb the air sufficiently to lift the exhaust from the chimney, thus obstructing the driver's vision with smoke.

[12]: 92, 94, 98, 100, 102  They were painted in the same shade of crimson lake which had already been applied to the Princess Royal class; the same style of horizontal lining that had been a feature of the first five locomotives was continued, but in gilt.

Although the crimson lake matched the standard LMS rolling stock, there was no attempt to apply the gilt lining along the sides of these coaches.

[15]: Plates 122 and 197  This equipment greatly helped the locomotive's fireman to meet the high demands for power during the non-stop run of 399 miles (642 km) between London Euston and Glasgow Central, when operating the Coronation Scot train.

Initially, locomotives that had previously been streamlined could be readily recognised by the sloping top to the front of their smokeboxes, as well as slightly smaller front-facing cab windows.

Prior even to 1910, it commenced installing Automatic Train Control (ATC), a system where each distant signal was accompanied by a ramp between the tracks with which a shoe on the locomotive would make contact as it passed over it.

The ensuing LMS top coats for the Coronation Class came in two basic colours during this period: Caledonian blue and crimson lake.

Linings for streamliners involved the renowned 'speed whiskers' comprising stripes emerging from a fixed point in the lower centre of the front of the locomotive to run in parallel along the sides.

6249–6255, constructed without streamlining, were also painted unlined black; the lettering and numerals on all these locomotives was in serif style coloured yellow with red shading.

46232, fresh in LMS-style lined black following its heavy general repair, was called back after a mere four days to be repainted blue.

[12]: 64, 186 British Railways undertook a massive programme to establish itself by repainting all its locomotives with their new BR numbers and replacing their previous corporate identity with its own.

[26]: 157 Because of insufficient clearance between the locomotives and the 25 kV overhead electric wires south of Crewe, the whole class was banned from operating under them with effect from 1 September 1964.

This came to an abrupt end when war was declared in September of that year, as the Government had decreed that in such an event all Britain's largest locomotives would be mothballed for the duration.

[15]: Summary of 'Duchess' 4-6-2 Allocation at Depots as at Autumn of the Years shown below During the 1960s the installation of overhead electrification commenced between London Euston and both Liverpool Lime Street and Manchester Piccadilly.

Just south of Crewe, the train (disputably)[36] achieved a speed of 114 miles per hour (183 km/h), narrowly beating the previous British record for a steam locomotive (held by the London and North Eastern Railway (LNER)).

Fortunately, Stanier had designed an inherently stable locomotive and both Coronation and its following train held the rails, although most of the crockery in the dining car was smashed, much to the consternation of the assembled guests[1]: 82–83 [7]: 26–31  In contrast to the LNER's record-breaking effort the previous year, when A4 Class No.

[7]: 46 [1]: 87  This sustained power output could not be expected on day-to-day service as it was beyond the shovelling capacity of a single fireman, and two firemen were carried for this test run.

46225 Duchess of Gloucester, a virtually identical sister engine, was tested by British Railways on the open road on the Settle and Carlisle line.

Strangely, the drawbar power output on the stationary test plant at Rugby could only be coaxed up to an absolute maximum of 1,710 hp (1,280 kW) which in retrospect casts doubt on the validity of the methodology.

Many years later, there was a degree of exoneration for driver Byford when the whole procedure was described as "the most inconsequential and unrepresentative series of competitive trials ever to be held on the railways of Great Britain".

[15]: Plates 26, 81, 95, 100, 145 and 201  Only one realistic mainline role was contemplated: to replace the Scottish Region A4 Class on the testing route between Edinburgh Waverley and Aberdeen.

[7]: 120  In 1975, following a slow deterioration due to Minehead's salty atmosphere, and the looming maintenance costs, Butlin's signed a twenty-year loan agreement for it to be taken under the wing of the National Railway Museum.

[7]: 142  After a substantial overhaul, the Duchess was declared fit in 1990 to continue working on the national network and at the same time the museum purchased it outright from Butlins.

The work was carried out at the railway workshops at Swanwick Junction and in July 2001 the restored locomotive was allowed a trial run on the national rail network, where it promptly broke down and had to be towed home.

[18]: 101, Plate 151 The city's love for its eponymous locomotive was borne out when, in 1953, Birmingham's Museum of Science and Industry determined that when the opportunity arose it would like to acquire No.

[52] It was modelled with a heavy diecast 'Mazak' body and chassis with tin-plate tender, and finished in LMS Crimson Lake livery; motive power was via a 12v DC electric motor for Hornby's 3-rail track system.

[52] After the collapse of the Meccano Ltd empire,[53] Wrenn acquired Hornby's Dublo tooling and continued to produce a variety of locomotives of the class in various liveries using the 'City' body from 1969 until the early 1990s.

Whitemetal and brass kits have been produced by various manufacturers including Keyser,[58] Jamieson,[59] Anchoridge and DJH,[60] who have offered streamlined and conventional outlines in a variety of gauges.