Initially asked in 1914 to study an overheating problem in rotary engines, Captain W. O. Bentley, an established car designer, developed a new and more efficient engine, with a weight-saving effect realized by careful design and the use of aluminum wherever possible. Equally important was the lower cost, as compared to the French Clerget, then widely used in British aircraft; and itself considered an improvement over the earlier Gnome

The initials A. R. 1 stood for Admiral Rotary 1, and was later renamed Model B. R. 1 for Bentley Rotary 1. The Humber Company of Coventry, England was the first to build the B. R. 1, and a larger model, known as the B. R. 2, was also manufactured by other firms. The A. R. 1 was used on aircraft such as the Sopwith F.1 Camel, Sopwith 7 F.1 Snipe, and Avro 504K.