The islands of Britain and Ireland lie adjacent to each other, and so their histories have always been complexly intertwined. Over the centuries there has been a considerable amount of migration back and forth between the two islands. In 1167 the Irish petty king Diarmait MacMurchada sought help in an internecine feud from the English king Henry II. This occasioned an Anglo- Norman incursion into Ireland and a large part of the island of Ireland came under English dominion as a result. Over the course of the next three centuries or so the area over which the English securely ruled gradually declined and many of the original settler families became ‘hibernicized’, adopting Irish customs, the Irish language, and the Irish system of law.

In the sixteenth century, various attempts were made to revivify England's presence in Ireland, frequently leading to war as the Irish resisted. When the English church broke with the church of Rome during the course of the Reformation in the sixteenth century, the majority of the Irish remained Catholic, so effecting an important distinction between the two populations. By the end of the sixteenth century the Irish leader Hugh O'Neill was at the head of an anti-English coalition which aimed, with the help of support from Catholic Spain, either to break or radically to reconfigure the link with England. Ironically, O'Neill had originally been sponsored by the English themselves and had visited the court of the English monarch several times. O'Neill was finally defeated and was forced into exile in 1607. His power-base had been in the northern Irish province of Ulster and the plan to impose control on this region included the assignment of large swathes of Ulster land to loyal subjects from Britain. By this point the English throne had passed to the Scottish king James VI, who reigned as James I in England and who sought to unify the island of Britain into a single kingdom. Under the settlement plan, a large amount of Ulster land was assigned to Scottish settlers - the ancestors of many of the Protestant families living in the north of Ireland today.