By far the most popular model to U.K farmers was, of course the "B". It originated in 1937 as a light general purpose machine which was of unit construction by adopting a reinforced "torque tube" to join engine to gearbox. This feature was to give the "B" a somewhat ' wasp'-like appearance and although small it could turn out 16HP at the belt.

Its popularity amongst farmers meant that the "B" was by far the most available AC model for restoration. Its small size meant that it was attractive to both ardent enthusiast and novice alike, as an addition to a collection or as a good starting point for the beginner.

The AC Model "B" had a good run, no doubt motivated by its popularity. Towards the 50's though it had started to become left behind, and not before time it was restyled around September, 1954 and called the D270 (UK). Contrary to popular belief the 270 was not a new model, the only difference was that the tinwork was changed and the engine power output was beefed up, by increasing the engine speed to around 1,650 rpm.

The final variation to the "B" came in the form of the D272 (UK) three years later. Again it was only a superficial change, receiving a new "shell" and despite the common statement that all 272's were diesels, about half in fact were still TVO.