They were introduced in 1904 for work on small branch lines.

The 4500 class was a later development with larger driving wheels.

The 4400s were particularly used in hilly districts, notably the Princetown and Much Wenlock Branches.

[2] The 4400, 4500 and 4575 classes, which all had 24 in (610 mm) stroke cylinders, the Standard 5 boiler and driving wheels under 5 ft (1.524 m), were collectively known as "Small Prairies", as opposed to the 5100, 3150, 5101, 6100, 3100 and 8100 classes, with 30 in (762 mm) stroke cylinders, Standard 2 or 4 boilers and driving wheels over 5 ft (1.524 m), known as "Large Prairies".

This article relating to steam locomotives operated in the United Kingdom is a stub.