27th June 1933. Pacifics.
Locomotives called Pacifics had a 4-6-2 wheel arrangement and prior to the 1923 railway grouping only 5 experimental Pacific Locos were built, the first being No.111 The Great Bear by Great Western in 1908. However they proved too powerful for then requirements as well as being too heavy for the infrastructure and were scrapped in 1924.
In the golden age of steam, LMS Railways introduced the prototype of its Princess Royal (Pacific) Class Locos which emerged from the paint-shop into service Today in 1933. It was designed by William Stanier for the West Coast run.
The second of the Class ‘out-shopped’ was Princess Elizabeth in November. They were built to haul the famous Royal Scot service from Euston to Glasgow Central. (1)
Enlarged locos came with the streamlined Princess Coronation Class between 1937-1948. Non streamlined locos comprised the ten known as the Duchesses-Hamilton, Sutherland, Abercorn etc., which were the heaviest express, passenger engines built in Britain and developed with the demand for extra power on the haul from London to Glasgow.(2)
Any streamlining was removed between 1945 and 1949 to facilitate maintenance. It is only useful anyway on a continuous high speed run, not always possible on the West Coast Route-it was a fashion of the 1930.s.
The London and North Eastern Railway(LNER) had inherited Pacifics from the Great Northern the A1, and North Eastern Railways the A2, which each built two Pacifics in 1922 with Classes of A1 rebuilt as A3 when after 1923, it became LNER.
In September 1935 the famous Nigel Gresley streamlined A4 Pacifics, were designed for high-speed passenger work and despite LNER not being especially profitable managed to produce the Silver Jubilee (to Newcastle) and Coronation Classes.(3)
Operating from London The Coronation, after which the Class was named, reached Edinburgh Waverley in six hours, at a record speed of 112 mph in 1935.
Many LNER Pacifics were named after birds: Golden Eagle, Osprey, Mallard etc the Directors of the LNERm and one after Gresley.
Finally they were named after Empire territories: Dominion of Canada, Empire of India and in wartime, Dwight D Eisenhower. Many are preserved.
In WWII Southern Railway introduced 2 Classes of Pacific Locos: the final Pacific design was BR Standard Class 8 Duchess of Gloucester.
What we have now is a monolithic locomotive design and it is only on preserved railways that the excitement of steam can be experienced.
(1) LMS was London Midland Scottish Railway. 12 Princess Royal Class were built with 1 rebuild in 1952.
LMS Pacifics Princess Elizabeth and Princess Margaret Rose are preserved at Butterley, Derbys.
(2) Twenty-one were named after cities served by the LMS and one after William Stanier. Duchess of Hamilton and Sutherland along with City of Birmingham are preserved.
(3) The first four of the class were allocated to 2509 Silver Link (scrapped December 1962), 2510 Quicksilver (scrapped April 1963), 2511 Silver King (scrapped at Motherwell, March 1965), and 2512 Silver Fox (scrapped October 1963)
Apart from Silver King the others were scrapped at Doncaster where they were built. Initially they were turned out in two-tone silver-grey and the class numbered 35 and all but one survived the Second World War.
Ref: wikipedia.org/Pic Princess Elizabeth and Great Bear.
Ref: wikipedia.org/princess_coronation_class/Pic of Duchess of Hamilton.
Ref: brdatabase.info.Princess Royal 6200 first in service 27.6.1933.