Ascertaining whether patents encourage invention necessitates understanding the incentives inventors respond to. The British patent system prior to its reform in 1852 was cumbersome and expensive. Whether it facilitated or delayed the Industrial Revolution is hotly debated. This paper's contribution is to examine the incentives to patent, and the characteristics of patentees, by observing the entire population of British patents granted up to the patent reforms of 1852. I find inventors patented widely because they had valuable inventions. Their value was positively associated with the skills and wealth of patentees. Inventors responded to demand-side conditions, and the system's expense did not hinder invention.