LNER O1 Class

The LNER O1 Class was the LNER classification for Robinson's Great Central Railway Class 8K 2-8-0 heavy freight locomotive after it was rebuilt by Edward Thompson in 1944–46, incorporating a new standard LNER B1-type boiler and revised cylinder arrangement to bring the ageing GCR design into line with current LNER practice. The O1 rebuilding was part of Thompson's programme of updating older inherited locomotive types, converting the ROD (Railway Operating Division) 2-8-0s that the LNER had purchased after the First World War into more standardised and maintainable form.

The original GCR Class 8K (LNER O4) had been one of the most important British heavy freight designs of the First World War era, with large numbers built for the ROD for military use on the Western Front and subsequently purchased by several British railways including the GCR and LNER. The O1 rebuild applied Thompson's standard B1 boiler to the O4 chassis, giving improved steaming and easier maintenance at the cost of significant rebuilding work. 58 examples were rebuilt as O1 from 1944.

The O1s continued on heavy freight duties under BR, working the coal and mineral traffic of the former-GCR routes and the general heavy freight on former-LNER main lines. One example of the related original O4 Class is preserved — 63601 at the Great Central Railway, Loughborough — representing the ROD 2-8-0 heritage. None of the Thompson O1 rebuilds specifically was preserved.