High Stakes by Dick Francis

Trainer Jody Leeds, father Quintin Leeds, Jockey Club member, is fleecing owner Steven Scott, when his horse Energise wins unexpectedly Steven is sure of his trainer's guilt and complicity with Ganser Mays, bookmaker in ringing (subsitituting identical horses, 'dead ringers', for the horses supposed to be running).  Steven has made a fortune making beautiful toys. Friend is Charlie Canterfield, merchant banker.  Steven has workshop in house and assistant come butler is Owen Idris.  Love interest beautiful intelligent American Alexandra Ward (Allie).  Steven realises Engerise has been swopped and decides to get him back, gets badly beaten but gets Energise back with a ringer scam of his own.