Raven's Shadow — Donald MacKenzie

When a bent London policeman carries out two ruthless murders, it is with the goal of making himself rich through the sale of stolen diamonds. And to cover his tracks he sets up an ingenious labyrinth of false covers and alibis. But when ex-cop John Raven is brought into the case by accident, it becomes a whodunit with Raven as detective in an exhilarating race against time.