LNWR Class G1

The LNWR Class G1, more widely known as the Super D, was a series of 0-8-0 heavy goods tender locomotives developed by Charles Bowen-Cooke at Crewe Works from 1912 as a superheated development of the earlier LNWR Class G (introduced 1901 under Webb), which became the London and North Western Railway's — and subsequently the London Midland and Scottish Railway's — standard heavy goods engine, built in large numbers and working the heaviest mineral and goods traffic across the LMS system from the Welsh coalfields to the Scottish border for nearly forty years.

Webb had introduced the LNWR's first 0-8-0 heavy goods engines in 1892 as compound types using his characteristic divided drive, and the subsequent simple-expansion Class G of 1901 under Whale was a significant improvement. Bowen-Cooke's G1 of 1912 added superheating to the Class G specification, giving substantially better steam economy and performance on the sustained heavy goods working that characterised the LNWR's traffic on the main lines across the Midlands and the North. The superheated G1 used Schmidt superheater equipment and Belpaire firebox, producing a robust and thermally efficient heavy goods engine well matched to the traffic needs of one of the busiest freight railways in Britain.

The LNWR's freight traffic was immense: coal from the South and North Staffordshire, Nottinghamshire, and Cumberland coalfields; iron ore to the Midlands furnaces; limestone from the Derbyshire quarries; steel goods from the Black Country works; and the general merchandise of the industrial North and Midlands that the LNWR carried to London and the south. On the Holyhead main line, the Trent Valley, and the routes over Shap and through the Lune Gorge to Carlisle, the G1 and G2 classes provided the muscle for the LNWR's heavy freight operation through the Edwardian and wartime years and well into the LMS era.

After the 1923 Grouping the LMS designated the G1 and its G2 variant (with larger boiler) collectively as LMS 7F 0-8-0, and continued them in service across the former-LNWR network throughout the 1920s and into the 1940s. One example, No. 49395, is preserved at the National Railway Museum, York, where it represents the Super D/G1 family and the LNWR's heavy goods tradition.