The 20/25 was the successor of the highly successful 20 hp Rolls-Royce Twenty introduced in 1922. The target market for the 20/25 was the same as the Twenty – the luxury, owner driver market. The project to develop the next generation 20 hp was code named Goshawk. The goal for the new model was to increase power & performance. This was achieved by increasing the bore size from 3 to 3.25 inches. The stroke was unchanged at 4.5 inches. This resulted in a 17% increase in capacity from 3128 to 3675cc – bring the RAC rating up to 25.4 hp.