Despite the initial success of the Merchant Navy class, their weight limited the routes they were allowed to use, and following the end of the war years, additional locomotives were required for main-line work.
Bulleid's solution was a slimmed down version of the 4-6-2 M.N. design.
Although money was tight, manufacturing for the War effort meant that at the cessation of hostilities, workshops were operating with machinery and staff, so production could start.
The design was not immediately distinguishable from the later batch of Merchant Navy class locomotives, adopting the same style air-smoothed casing with smoke deflectors, and 6 ft 2 inches diameter driving wheels.
But the 3 cylinders of reduced diameter produced a slightly lower tractive effort of 31,050 lbs, and their shortened length of 67 ft. 4¾ inches allowed them to be 5 tons lighter.
And unlike the double framed tenders of the Merchant Navy class, the light weights had a single frame tender chassis, similar to the Q1.
The first of the class, 21C101 'Exeter' was outshopped from Brighton works in 1945, and the initial batch was allocated to the West of England.
Here there was a need for new motive power, and locomotives were fittingly named after local places and towns.
As production continued, later batches were allocated to the eastern area, these named after R.A.F. Squadrons in recognition of their War effort.
Construction continued after Bulleid had left for Ireland, and into Nationalisation; in all 110 examples were built, split between the 'West Country' and 'Battle of Britain' naming.
The last class member 34110 '66 Squadron' was completed in 1951.
The specification was similar, excepting that the last 40 locomotives cosmetically had 9' 0" wide cabs, and larger 5500 Gallon tenders.
Perhaps famously, several Bulleid light pacifics performed very well in the post-Nationalisation locomotive exchanges of 1948.
For this, the cream of locomotives from the four companies were run on 'foreign metals' over the summer months, so their characteristics could be compared.
Representing the Southern Region, the Bulleid light pacifics proved to be the performance sensation of the trials - though one might want to exclude the matter of coal consumption.
Following Nationalisation many of the light pacifics were rebuilt - in the same manner as the Merchant Navy class - removing the air-smoothed casing and sometimes troublesome enclosed valve gear.
However, with dieselisation on the horizon, only about half the class were altered, examples like 34006 keeping their original form until scrapping.
In all, 43 'West County' and 17 'Battle of Britain' class locos had been rebuilt by the end of the programme in May 1961; the last to be outshopped was 34104 'Bere Alston'.
Used for passenger and freight workings, the class continued to serve uneventfully, some remaining to the end on 10th July 1967, when all Southern Railway steam was withdrawn.
Fortunately quite a few 'light pacifics' that were sent to Barry for scrapping survived the cutting torch, so quite a few have made it through to preservation, although in varying states of repair.
In December 2006 unrebuilt No. 34007 'Wadebridge' was put back into steam for the first time since scrapping.
During September 2008 restored 'Manston' pulled its first passenger train on the Swanage Railway, and the same month also saw the return to traffic of No. 34046 'Braunton' after restoration by the West Somerset Railway.
34010 Sidmouth started a full restoration from scrapyard condition in early 2016, perhaps the last one to receive a chance to steam again.
A summary of which class members still exist can be found on the Survivors page.
Considering this was numerically Bulleid's largest class, live steam models of 'light pacifics' are relatively rare, and I've only tracked down a handful in passenger hauling sizes, most still under construction.
This is a potentially ambitious locomotive to build, and there are currently no commercially available drawings for the light Pacifics.
So, the small number of examples constructed result from a long hard look at Works drawings, and scaling the dimensions.