The prototype was designed by the LNWR for heavy mineral traffic. The G2As were the final development of a long line of LNWR 0-8-0 locomotives (totalling 836 in all), dating back to 1892, when Webb was designing LNWR locomotives. This particular version was developed immediately before Grouping, in 1923, during the period that Beames was CME.

The G2As were converted from G1s and, in LMS days, were fitted with Belpaire fireboxes, a process which continued into the BR period. They ran with a Bowen-Cooke tender. Built as heavy goods engines, the LMS Class 8F took over much of their work but there were still 478 former LNWR 0-8-0s handed over to BR in 1948. The last member of the class was withdrawn in 1964. In both the LMS and BR eras the locomotives were always painted plain black.