The locomotives quickly proved themselves to be so useful that they were produced more or less continuously in a series of batches (or lots) over a twelve-year period (1911–1923), sometimes incorporating detailed differences.

[4] Three further batches, totalling a further forty locomotives (4321–4360) were built at Swindon and delivered June 1913 and May 1914, before the onset of the First World War impeded further production.

These locomotives (and all subsequent examples) had frames lengthened by 9 in (229 mm) at the rear to give better access for maintenance as well as providing more room in the cab.

From 1917 detailed changes were made to the design giving better weight distribution between the wheels which were later applied to other members of the class.

[5] Eleven examples of the class were transported to France during World War I in the service of the Railway Operating Division of the British Army and these were 5319–5326 and 5328–5330.

Lot 216 was for a further 28 locomotives (6342–6369) but Swindon works was then unable to keep pace with the demand for them and only the first twenty were completed after delay, between March and December 1923.

As Swindon works could not keep pace an order was placed with Robert Stephenson and Company in 1921 for fifty locomotives (Nos.

In 1932, Collett built a further twenty examples (9300–9319) to a modified design with side window cabs, outside steam pipes and a screw reverse.

After passing into British Railways ownership, these locomotives were modified back to light buffer beam design and were renumbered 7322–7341 between 1956 and 1959.

In November and December 1927 additional weight was added to the front end of four examples so that the pony truck would be forced to impart more side thrust to the main frames on bends.

These locomotives reverted to their original state, but between January and March 1928, 65 engines of 5300 series received additional weight on the pony truck, and 3000 was added to their running numbers, temporarily creating an ‘8300 Class’.

Employing a Standard number 4 boiler and the support struts similar to those fitted to the '2800' class, the class very quickly earned an excellent reputation in its ability to handle most types of traffic, from local stopping goods to main line expresses.

Nock they "could handle the heavy goods work as well as the 'Aberdares' and could run up to 70 mph with passenger trains, in other words they were the ideal mixed traffic locomotive".

The experiment, encouraged by the government was abandoned in 1948 once the extra maintenance costs were calculated and the bill had arrived for the imported oil.

It was intended to replace the whole class in this way but the advent of the Second World War in 1939 brought a temporary halt to withdrawals and the programme was never revived.