The GWR class 4800 was a 0-4-2T locomotive designed by Collett for passenger service on branch lines, especially with “autocoach” driving trailers. For this it was equipped with a mechanism that allowed to operate the regulator of the locomotive from the cab of the autocoach. A reverser to operate the valve gear was only available in the locomotive, so that the fireman had to operate this according to bell signals from the driver.

It was not only designed to replace Armstrong's class 517, but was also directly based on this 64 year-old design. After the class 517 had received several improvements over the years, it was finally rebuilt by Collett from 1922. Ten years later, the new class had many similarities with the rebuilt class 517. Among these were larger cylinders and the new boiler with a Belpaire firebox and a higher pressure. Between 1932 and 1936, 75 locomotives of the class 4800 were built at Swindon. These locomotives often operated with only one autocoach and many sources state that they were capable of speeds of up to 80 mph or 129 km/h.

In 1933, 20 more were built without autocoach equipment, which became the class 5800. In 1946, the class 4800 was renumbered to 1400 since some class 2800 locomotives had been rebuilt to oil firing and were now numbered in the 4800 range. The class 5800 was already withdrawn between 1957 and 1961, as there were not many tasks for these small locomotives without autocoach equipment. Their class 1400 cousins were only withdrawn between 1956 and 1965. Four have been preserved, of which two are still in working order.