Bristol had originally intended to use the Aquila and Perseus as two of its major designs in the 1930s, but the rapid increase in size and speed of aircraft in the 1930s demanded much larger engines than either of these. The mechanicals from both of these designs were then put into two-row configuations to develop much larger engines, the Aquila becoming the Taurus, and the Perseus becoming the Hercules.
Unlike the earlier engines, where the sleeve valve was a new and untried design, the Taurus was fairly well understood and was delivered running at almost the same power it ended with, at 1,015hp. After several years of development, this improved only to 1,130hp, a tesimonial to how good the first versions were.
The first Taurus engines were delivered just before World War II opened, and found some use primarily in Bristol's own Beaufort torpedo bomber. When the same plane was fitted with the famous Pratt and Whitney R-1830 Twin Wasp, its performance actually fell even though the Twin Wasp was both lighter and more powerful.
Nevertheless by the time the engine was in widespread production, designs had already demanded even higher power settings. The Hercules went on to see fairly widespread use, while the Taurus ended with the Beaufort after only a few years.