This design was specified by the Locomotive Superintendent of the Shrewsbury & Chester, Edward Jeffreys, and built by the Vulcan Foundry. Four were ordered in 1852, and delivered in 1853. They were double framed, and quite powerful locomotives for the time. In the meantime Jeffreys had left the Shrewsbury & Chester and was now Locomotive Superintendant of the Shrewsbury and Hereford. Four more of the design were built for the S&H in 1853/4. The S&C locomotives came to the GWR in 1854. The S&H locomotives had a more complex ownership (pay attention, this is like the three card trick), In 1862 the GWR (1/4 share), the LNWR (1/2 share) and the West Midland Railway (1/4 share) jointly leased the S&H. The locomotives went half to the LNWR and half jointly between the GWR and WMR, and these 0-4-2s went to the GWR/WMR. Then in 1863 the GWR took over (formally amalgamated with) the West Midland, and so all eight were now GWR locomotives.
No 30 was destroyed in a boiler explosion in 1859 and a new No 30, most likely incorporating usable parts from the old, was built the next year. They were never renewed or received major rebuilds and scrapped from 1870-5.
There's a sort of grim fascination about the enormous variety of these very early locomotives and their changes and rebuilds. I can imagine a keen scratchbuilder getting quite excited about all the possibilities. One would certainly never run out of subjects. From my point of view there's a large number of drawings required to do reasonable justice to the 19thC GWR scene. At a guess it's going to be well into three figures, and some will be very tricky to manage because of limited data, especially the Wolverhampton rebuilds, for which there are some photographs but few drawings. One can only admire the dedication of Ahrons, who drew so many of the early engines by hand for an article in 'The Locomotive'. I can only hope they paid better than modern book publishers!