The Great Western Railway 4000 or Star were a class of 4-cylinder 4-6-0 passenger steam locomotives designed by George Jackson Churchward for the Great Western Railway (GWR) in 1906 and introduced from early 1907.

During the first decade of the twentieth century, the new Chief Mechanical Engineer, George Jackson Churchward designed or acquired a number of experimental locomotives with different wheel arrangements and boiler designs to help him plan for the future motive power needs of the railway.

[5] Following the success of the prototypes of his two-cylinder Saint class 4-6-0 locomotives, introduced in 1902, Churchward became interested in developing a more powerful 4-cylinder type for the longer non-stop express services.

He therefore persuaded the GWR to acquire three French 4-cylinder 4-4-2 compound locomotives, 102 La France (1904) and 103 President and 104 Alliance (both 1905) for comparison purposes.

As with some early members of the Saint class it was built as a 4-4-2 but designed so that it could easily be converted to a 4-6-0.

During initial trials the prototype proved to be largely successful although Charles Rous-Marten commented that 'there were indications that with heavier loads, and less favourable weather, greater adhesion would be needed.

[9] Seven series of what would later be known as 'Star Class' locomotives built between 1907 and 1923 each of which contained detailed differences from the others The first series of ten locomotives were built at Swindon in 1907 (Lot 168) numbered 4001–4010 and named after well-known Stars, perpetuating the names of the earlier broad gauge GWR Star Class of 1838.

A second series of ten similar locomotives appeared in 1908 (Swindon Lot 173), with improved bogies, numbered 4011–4020 and named after historical knights.

A third series of ten further locomotives appeared during 1909 (Swindon Lot 178), numbered 4021–4030 and named after British Kings.

Once this was proved to be beneficial, this size gradually became the standard for the class, as they visited the works for their periodic overhaul.

The GWR experienced a substantial growth in long-distance passenger traffic immediately before the First World War requiring a further series of fifteen locomotives during the first six months of 1914 (Swindon Lot 199).

They were all built with 15 in (381 mm) diameter cylinders and had improved boilers compared to the previous batch.

4063–4072 were all rebuilt as Castle Class locomotives, being renumbered 5083–5092 but retaining their original names.

Members of the class performed well as passenger locomotives over all the long-distance routes of the GWR on the fastest express trains and those requiring the longest distance between stops.

They gradually became displaced to secondary services by members of the Castle and King classes in the late 1920s and 1930s.

[16] According to le Fleming "their performance was consistently of the highest standard and they were remarkable free-running engines which rarely suffered breakdown in service.

'"[17] As already noted, between 1925 and 1940 Churchward's successor Charles Collett ordered fifteen examples to be dismantled and their parts used in the construction of new Castle class locomotives.

In 2010 Lode Star was moved to Steam Museum in Swindon, as a static non-working exhibit.