Midland Red was in the vanguard of bus design when its own BMMO S6 underfloor-engined single-decker entered service in 1946. Development continued, however, including accommodating increases in vehicle dimensions. Firstly buses could become 8 feet wide (appropriately known as the S8), an extra six inches, and by 1950 model numbers had moved up to S12, the first design of thirty-footer (an increase of two feet six inches). Body contracts to BMMO design on all these early postwar single-deckers, which totalled 500 vehicles, were split between Brush and Metro-Cammell. All the earlier production underfloor-engined single-deckers were subsequently rebuilt to the new length, mostly by Roe, to achieve the capacity of the S12.

3750 was new to Midland Red's Swadlincote garage. The S12 was withdrawn from PSV in August 1966, before being used as a Driver Trainer. Its last year was at Worcester depot before withdrawal in February 1970.

Upon withdrawal, 3750 was passed to the Digbeth S12 Group for preservation and was rallied extensively before being parked up for many years. A lot of restoration work was carried out by Reliance Bus Works until 3750 passed to Transport Museum Wythall in December 2024.