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.

3744 spent many years at Midland Red's Sutton Coldfield garage. Its last year was at Stourbridge before withdrawal in September 1964. It was fairly unusual for a BMMO product to find a second owner because spares were not readily available. 3744, however, passed to the Automotive Products Group of Leamington Spa. It was repainted black and white for its new duties as a mobile research unit based at AP's Shenington test area. Fortunately AP approached the Museum when the bus was retired in 1981. Work has recently been carried out to improve its exterior appearance but a full restoration is still required.