Rolls-Royce R engine was invaluable in the subsequent development of the Rolls-Royce Merlin engine and the Spitfire. A de-rated R engine, known as the Griffon, was tested in 1933, but it was not directly related to the production Rolls-Royce Griffon of 1939, of the same exact bore/stroke and resultant displacement figures as the "R" design. Three examples of the R engine are on public display in British museums as of 2014. Rolls-Royce realised that the Napier Lion engine used in the 1927 Supermarine S.5 Schneider Trophy winner had reached the peak of its development, and that for Britain's entrant in the next
Rolls-Royce Limited engine. When World War I broke out in August 1914, Rolls-Royce (and many others) were taken by surprise. As a manufacturer of luxury cars, Rolls-Royce was immediately vulnerable, and Claude Johnson thought the bank would withdraw its overdraft facility on which Rolls-Royce depended at that time. Nevertheless, believing that war was likely to be short-lived the directors initially decided not to seek government work making aero engines. However, this position was quickly reversed and Rolls-Royce was persuaded by the War Office to manufacture fifty air-cooled V8 engines under licence from Renault. Meanwhile, the Royal Aircraft Factory asked Rolls-Royce to design