Editing GWR 4000 Class (section)

==Modifications==
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.
Throughout their careers the remainder of the class was subject to detailed modifications and improvements to their boilers, smokeboxes, and steam pipes so that "the only period when the appearance of the class was approximately uniform was from 1925 to 1927".<ref name=RCTS4>{{harvnb |le Fleming|1953 |p=H9}}</ref> {{convert|4000|impgal|abbr=on}} [[tender (rail)|tender]]s were also fitted from 1938 onwards.