Bonecrack by Dick Francis

Neil Griffon takes over the training of horses at his father's stable after his father is hospitalised with a broken leg.  He is visited by vicious sociopathic crime boss Enso Riviera who has only one aim, to make Neil put his son Alessandro the jockey on Archangel the favourite for the Derby, by any means necessary.  Griffon's head lad is Etty Craig, great female character.  Neil takes on Alessandro and a dangerous game begins, Neil trying to keep his life and his father's stables alive under paternal pressure that he does not know what he's doing.  Set in Newmarket.  Ends with attempted shooting of stable lead jockey Tommy Hoylake on Newmarket Heath.