This article assesses the utility of the British monarchy as a hegemonic institution consolidating the British state from the mid-nineteenth to the early twentieth centuries. It does so by examining its relationship with the 'Celtic' regions - Ireland, Wales and Scotland. It was a relationship that fluctuated over this period. While a close personal as well as constitutional relationship existed between the monarchy and Scotland during the reign of Queen Victoria, as against her more distant - even antagonistic at times - relationship with Ireland and Wales, the personal dimension to monarchical allegiance underwent significant change under Edward VII and George V, with Ireland and, to a lesser extent, Wales, a closer focus of royal attention as these regions apparently posed serious threats to state stability in the early twentieth century. the article demonstrates how the monarchy's relationship with the 'Celtic' regions was shaped by a variety of interacting factors - historical, socio-economic, constitutional, political and personal - that illustrated its strengths and weaknesses. Thus a combination of reform and royal conciliation could function to unite Ireland with Scotland and Wales in defence of King and country in 1914, while the troubled post-1916 period posed problems royal influence had greater difficulty addressing. Nevertheless, the monarchy was a central institution in the constitutional settlement of 1921, which served to maintain, if in changed circumstances, its relationship with the three 'Celtic' regions.