The 4AC Roadster
Externally, the 4AC was virtually identical in bodywork to the 4AB and the 4AD. However, the 4AC never actually saw full production, being simply a prototype with only a handfull of about 12 or 13 of them ever being built. The 4ACs were sometimes referred to as Bantam Roadsters and apparently some of them did carry the Bantam boot badge.
The fundamental difference between the 4AC and the 4AB/AD was under the bonnet, where it had a 1200cc engine, in place of the 1047 cc. power plant. The upgrade was as a result of Singer wanting to rationalize their engine production facilities. After the war, the company had introduced the SM 1500 Saloon, with its all new short stroke 1500 cc. engine. In order to economize, they simply took the same block, but reduced the bore to build a 1200 cc engine, thus creating the 4AC.