The distinctive designs by James Pearson, the railway company's engineer, featured single large flangeless driving wheels and two supporting bogies. The water was carried in both well and back tanks, leaving the boilers exposed in the same way as tender locomotives.
The three types are distinguished by the size of driving wheel; the early 9-foot-diameter (2.7 m) wheels being replaced by smaller ones on later designs.
16.5 in × 24 in (419 mm × 610 mm) or
17 in × 24 in (432 mm × 610 mm)
12 (1862–1885) GWR No. 2005
29 (1859–1880) GWR No. 2006
These two locomotives were built as replacements for more conventional 2-2-2 express passenger locomotives with 7-foot-6-inch (2.29 m) driving wheels and were given wheels of this same size, rather than the 9-foot-diameter (2.7 m) wheels of their 4-2-4T predecessors.
No. 29 was the first locomotive built at the Bristol and Exeter Railway's new Bristol workshops in 1859. It had slightly larger 17-inch-diameter (430 mm) cylinders and a 25-foot-21⁄2-inch (7.684 m) wheelbase. When withdrawn in 1885 it was the end of Pearson's 4-2-4Ts.
No. 12 followed in 1862 and returned to 161⁄2-inch (420 mm) cylinders and had a slightly shorter 25-foot-1-inch (7.65 m) wheelbase.
Four of the 9-foot locomotives were replaced by these "renewals", built in the Bristol and Exeter Railway workshops at Bristol. A pair of their new 8-foot-10-inch-diameter (2.69 m) driving wheels can be seen at Swindon Steam Railway Museum.
No. 39, recently renumbered as GWR 2001, derailed at Long Ashton near Bristol on 27 July 1876 and was withdrawn from service. While the poor condition of the track was a contributing factor, it was decided to rebuild the remaining three express 4-2-4Ts to more conventional 4-2-2 tender locomotives.