[1] With coal trains increasing in size and scale, the GWR needed to develop a more powerful locomotive to meet these requirements, on what were relatively short haul routes.

After proposing a 2-8-2T design, Churchward developed the UK's first 2-8-0 tank engine, through concerns that the longer frames required for a 2-8-2T would restrict operation in the South Wales Valleys.

In 14 months of testing, it easily proved itself capable of negotiating curves down to 2 chains (130 ft; 40 m) in radius.

However, due to the Stock Market Crash of 1929, and a resultant down turn in coal exports to Europe, a number of the 4200 Class having been returned to Swindon for overhaul, had in fact been stored there.

To increase their operational ability across the wider GWR network, Chief Engineer Charles Collett took the board-agreed decision to alter this batch in production to 2-8-2T by adding a bolt-on 4 feet (1.22 m) extension to the frames to accommodate a pair of rear trailing wheels, which took the coal capacity up to 6 tons and water tanks to 2500 gallons.

[1][2][4] Although operationally banned from certain goods yards, most 7200's found work across the GWR system, mostly deployed on iron ore and stone trains from Banbury.

[5] In later years many of the remaining 4200s were upgraded to 5205 specification with outside steam pipes, larger cylinders and in some cases curved frames at the front end.

[6] Five have been preserved, with all rescued from Woodham Brothers scrapyard in Barry, Vale of Glamorgan, South Wales.