The area under English rule and law grew and shrank over time, and reached its greatest extent in the late 13th and early 14th centuries.

The fluid political situation and Norman feudal[3] system allowed a great deal of autonomy for the Anglo-Norman lords in Ireland, who carved out earldoms for themselves and had almost as much authority as some of the native Gaelic kings.

It owed its origins to the decision of a Leinster dynast, Diarmait Mac Murchada (Diarmuid MacMorrough), to bring in a Norman knight based in Wales, Richard de Clare, 2nd Earl of Pembroke (alias 'Strongbow'), to aid him in his battle to regain his throne, after being overthrown by a confederation led by the new Irish High King (the previous incumbent had protected MacMurrough).

Religious practices and ecclesiastical organisation in Ireland had evolved divergently from those in areas of Europe influenced more directly by the Holy See, although many of these differences had been eliminated or greatly lessened by the time the bull was issued in 1155.

In the process he accepted the fealty of the Gaelic kings at Dublin in November 1171 and summoned the Synod of Cashel in 1172, this bringing the Irish Church into conformity with English and European norms.

For he had divided his territories between his sons, with the youngest being nicknamed Johan sanz Terre (in English, "John Lackland") as he was left without lands to rule.

It had been a common practice for the Norman lordships as well as government forces to recruit the native Irish who were allied to them or living in English controlled areas (i.e. Leinster including Meath and Ossory, Munster and some parts of Connacht).

This was easy to do as the native Irish had no great sense of national identity at that time and were prone to mercenarism and shifting alliances.

Some of the more notable among those clans who had formerly cooperated with the English but became increasingly alienated until turning openly anti-Norman and a thorn in the side of the Dublin administration were the O'Connor Falys, the MacMurrough-Kavanagh dynasty (Kingdom of Leinster), the Byrnes and the O'Mores of Leix.

These clans were able to successfully defend their territories against English attack for a very long time through the use of asymmetrical guerrilla warfare and devastating raids into the lands held by the colonists.

Most clans remained loyal to the Crown most of the time, at least in theory, but using a Gaelic-style system of alliances based on mutual favours, centered on the Lord Deputy who was usually the current Earl of Kildare.

The end of this rebellion and Henry VIII's seizure of the Irish monasteries around 1540 led on to his plan to create a new kingdom based on the existing parliament.

Henry VIII also wanted Ireland to become a full kingdom to encourage a greater sense of loyalty amongst his Irish subjects, some of whom took part in his policy of surrender and regrant.

[9] This grant would not work as Paul IV had expected, as Mary died in 1558 and was succeeded as Queen of England and Ireland by her half-sister Elizabeth I, a Protestant.