Mr Darley's Arabian traces an extraordinary bloodline of outstanding racehorses - 95% of all thoroughbreds in the world are descended from one horse, the so-called Darley Arabian, shipped from Aleppo to Yorkshire in 1704 by a second son who failed to make his fortune and died before he could follow his horse home. Chris McGrath tells the story of the men and women who owned and traded and bred the horses descended from that first stallion. He also follows the men they hired to train them, and the jockeys who rode them, and sometimes rescued them from the knacker's yard, unwittingly preserving the genetic line of winners that currently resides with the champion Frankel.