BRCW obtained an order for 20 mixed traffic diesel-electric locomotives powered by 1,160 hp (870 kW) Sulzer 6LDA28 engines.

The Birmingham Railway Carriage and Wagon Company was a rolling stock manufacturer, although they were building diesel multiple units for BR.

The Pilot Scheme batch of twenty locomotives (D5300-5319, Class 26/0) were delivered to Hornsey TMD (Traction Maintenance Depot) on the Eastern Region of British Railways between July 1958 and March 1959.

This was the precursor to a further twenty seven locomotives of a slightly modified design (D5320-5346, Class 26/1) being delivered to the Scottish Region between April and October 1959.

The first two of these locomotives were briefly allocated to Leith Central, but subsequently all of the Scottish batch were based at Haymarket TMD (although some went to Hornsey on loan for a time).

One notable duty, shared with locally based Class 24s, was to operate 'The Royal Highlander' Inverness to London Euston sleeping car express as far south as Perth, a demanding turn which required three locomotives working in multiple.

The Haymarket engines were latterly more associated with goods traffic, and the first seven locomotives (D5300-5306, later renumbered 26007, 26001–006) were given slow speed control apparatus in 1967 for use on MGR coal trains to the then new Cockenzie Power Station.

In August 1992, the remaining engines were reallocated to Inverness, although this was essentially a paper exercise as locomotives only returned to their home depot for major maintenance.