At The Society of Border Leicester Sheep Breeders' site, I learned:
Robert Bakewell followed on the work of arable pioneers Jethro Tull and Lord “Turnip” Townshend but it is in the field of livestock and especially sheep that Bakewell particularly excelled. At this time all sheep were run together, breeding at random resulting in many different breeds all with their own unique, but random characteristics. Bakewell segregated the sexes, allowed mating only to occur deliberately and specifically. He developed a system of breeding termed “in-and-in”, breeding animals of close relationship with each other or line breeding as it is known today. It is thought he started with the old Lincolnshire breed crossing them with the best of the local Leicestershire types and then by breeding “in-and-in” coupled with rigorous selection and culling was able to fix desirable characteristics for improved meat quality and production through pre-potency. This resultant breed Bakewell called the “New Leicester” becoming known as the “Dishley Leicester”.
And at Wikipedia, I learned that he greatly improved the taste of mutton. Not a bad epitah.