 The British monarch was head of state of all of these states and countries of the archipelago from the Union of the Crowns in 1603 until their role in Ireland became ambiguous with the enactment of the Constitution of Ireland in 1937.The remaining functions of the monarch in Ireland were transferred to the President of Ireland, with coming into effect of the Republic of Ireland Act in 1949.Several academic perspectives are important in the study and understanding of Ireland–United Kingdom relations.