The constitutional union of 1800 was an extreme political formula. It was pursued with ruthless energy; it ultimately disappointed its architects. Yet the Union provided a constitutional framework for Ireland for 120 years, and has survived in a truncated form within Northern Ireland since 1920. The Belfast Agreement of 1998, which is sometimes viewed as a 'renegotiation' of the Union, has brought into focus the issue of its survival. More than ever, there is a need to understand not only why the original Union failed in 1920-21, but also how and why it lasted for over a century. More than ever there is a need to illuminate some of the explanations for the survival of the British state in nineteenth-century Ireland and beyond.

Yet even though the Union was a central feature of political life in the nineteenth century modern Irish historians have some how evaded the question of its survival. At one level the reason for this is not hard to locate: modern Irish political historiography remains dominated by the Home Rule and revolutionary era; and it is hard to escape the impression that a good deal of Irish history writing has, as its ultimate destination, the political settlements of the early 1920s, when the Irish Free State and Northern Ireland were each established. Of course this is an entirely unexceptional emphasis, given the enormous and lasting significance which the revolutionary and Ulster Unionist movements possessed. It is also entirely reasonable that Irish historians should emphasise the ultimate failure of the Union in the twenty-six counties. But it is possible that this reasonableness has created a paradox – that many Irish historians have effectively dedicated themselves to explaining the death of a settlement which (whatever the quality of its life) clung on for a remarkable length of time.