Whale began rebuilding the Webb 0-8-0s in August 1904, and the alterations took several forms. The first to appear were converted from Class B, which Whale considered to have an excessive front overhang: the principal change was the addition of a pony truck, making a 2-8-0; they remained as four-cylinder compounds, and between August 1904 and October 1908, 36 locomotives were converted. 26 of these retained their original boilers and were later designated Class E; ten of those converted from May 1906 were provided with larger boilers (of the type used on the "Experiment" class) and were later designated Class F. Two of those initially converted to Class E were later given the larger boiler, and joined Class F.