This book explores the apex of the Roman Republic, positing that the Republic has been one of mixed characteristics combining monarchic, oligarchic, aristocratic and democratic elements in its constitution. It offers unique analytical insights into the golden constitutional era of the Roman Republic by exploring the essence, the fundamentals, the historical roots and the structures of its institutions. In addition to exploring the apex of the Republic and the reasons behind it, the monograph taxonomises and explores the constituent elements of the Republic. It does so by offering a detailed analysis of the precise constitutional nature of the Roman Republic and its institutions in the same period of time. Moreover, the book radically challenges the traditional picture of the Roman republic as a three-dimensional constitutional reality (monarchy – aristocracy – democracy), proposing that the Republic was more complex than that, as in it being a four-dimensional constitutional reality (monarchy – aristocracy – oligarchy – democracy).