[nathanbedford]

DNA evidence, for example, suggests that most Indigenous horses had descended from Spanish and Iberian horses, with British horses becoming more common in the 18th and 19th Centuries.

Iberian horses, of course, suggests a strong Arabian influence introduced by the Moors that bore the wonderful traits of those horses, endurance, density of bone, bottom, and intelligence. There is scarcely a breed in the world that is not improved by introduction of Arabian blood. By the 18th and 19th century the British horses referred to already had Arabian genes already bread into many.

[SunkenCiv]

95% of thoroughbreds linked to one superstud
By John Pickrell
6 September 2005
https://www.newscientist.com/article/dn7941-95-of-thoroughbreds-linked-to-one-superstud/