"I'm on a mission to make GB great in its own right." A statement from Britain's new prime minister, perhaps? No. Forget Westminster, and cast your mind instead to the rolling Cotswold hills that frame the area around Cheltenham. Those words are uttered not far up the road from the home of National Hunt racing, at Overbury Stud, by the new owner of the stud's newest stallion. Jayne McGivern is unashamedly proud of her recent purchase of Golden Horn (GB), the horse who lit up the 2015 Flat season, graduating...