Enter pale death - Barbara Cleverly

One morning before dawn at her regal country estate, Lady Lavinia Truelove is crushed to death by a horse. Classified as death by misadventure', this appears a gruesome accident, but Scotland Yard Detective Joe Sandilands suspects foul play. His suspicions are aggravated by his personal grievances toward Sir James Truelove, Lady Lavinia's widower and the influential academic patron of Dorcas Joliffe, whom Joe one day hopes to marry. As Joe's investigation yields surprising secrets about one of England's most powerful families, he discovers secrets about Dorcas.'