The Great Western Railway 3200 Class (or 'Earl' Class) was a design of 4-4-0 steam locomotive for passenger train work. The nickname for this class, almost universally used at the time these engines were in service was Dukedog since the locomotives were composed of former Duke Class boilers on Bulldog Class frames. As such they were one of the last standard gauge steam locomotive classes to retain outside frames.

The GWR absorbed the Cambrian Railways in 1923, but, with the Cambrian main line being lightly built, permanent way restrictions debarred the use of heavier locomotives. This meant that only a few classes of GWR locomotive were allowed to run over it, including the Duke Class. However, by the 1930s the Duke class engines were past their estimated life, and in particular the frames were in poor condition. At the same time the heavier Bulldog Class was becoming redundant and being withdrawn, and later members of this class had an improved straight topped frame design.

In December 1929, Duke No.3265 Tre Pol and Pen was withdrawn, and the cab and other above-frame fittings together with a spare Duke boiler and smokebox, were fitted to the straight-topped frames of Bulldog no. 3365 Charles Grey Mott. The rebuilt locomotive was given the name and number of the Duke. This resulted in an engine with stronger frames which could still be used on yellow weight restricted routes.  The conversion was a success and from 1936 twenty-nine "new" locomotives were constructed from the relevant components of withdrawn Dukes and Bulldogs. A further eleven conversions were scheduled, but the onset of World War II brought a halt to the program.

30 were rebuilt, 1 survived and has been preserved directly from BR.