The English invasion of Ireland in 1169 was in many ways an extension of Welsh marcher politics. Barons who had enjoyed the wholehearted support of the English king in their conflicts with the Welsh were constrained from 1166 by a royal policy based on compromise rather than conquest. A new adventure in Ireland offered them a chance to replicate across the sea what they were losing in Wales. Nevertheless, from the reign of King John, successive English kings sought to export the apparatus of the English state to this new frontier to better exploit its resources for their wars in France and Scotland. By the time that Roger Mortimer and Joan de Geneville inherited the liberty of Trim at the beginning of the fourteenth century, Irish politics was driven not only by the frequent wars amongst the Gaelic and colonial populations (which were not always defined along ethnic lines), but also by the competing forces of royal administration and aristocratic endeavour. Roger was at the very heart of this process as head of the Irish administration from 1316, but his commission also required him to defend the island against an invasion from Scotland. Robert Bruce and his brother Edward sought to outflank Edward II of England by opening up a new theatre of war in Ireland. They also sought to deny him the Irish resources that helped to sustain his campaigns into Scotland, and ultimately to establish a Bruce kingdom of Ireland. Ireland, therefore, was integral to British politics in this period; and Roger Mortimer was at its very heart. Dr Colin Veach is a Senior Lecturer in Medieval History at the University of Hull and a fellow of the Royal Historical Society. Here he talks about the Mortimer's in Ireland.