Racehorse trainer Mark Johnston is a lynchpin of British flat racing. In August 2018 - when 20-1 shot Poet's Society, ridden by Frankie Dettori, streaked to victory at York - Mark became the most prolific winning trainer in British racing history, saddling 4,194 winners. Based in a 300-acre training yard in Yorkshire, he has never trained fewer than 100 winners each season for the last 26 years including champions such as Attraction, Mister Baileys, Double Trigger and Shamardal. Mark grew up on a council estate in East Kilbride and learned to ride when he was a child. His father was a horse lover who enjoyed a flutter and took the young Mark to the bookies when he placed his bets - although Mark was too young to go inside. As a 14-year-old Mark raced whippets and later studied veterinary medicine at Glasgow University but his dream was always to become a racehorse trainer. In 1986, together with his wife and business partner Deirdre, Mark bought his first yard. He had no money or connections in the racing world and had three-and-a-half paying horses rather than the 12 he needed under the terms of his trainer's licence. In these early days, the horses trained on a nearby beach that doubled up as an MOD bombing range. Johnston horses are known for their front-running style - he believes races aren't won by horses accelerating and passing the other runners, but when the horses in front slow down. He says: "I tell my jockeys to bowl along at the speed the horse is happiest." Presenter: Lauren Laverne Producer: Paula McGinley