Between the 13th and 15th centuries English power diminished significantly in Ireland for three primary reasons. Firstly, there was a reconsolidation and resurgence in the power of the Irish kingdoms which had been shattered during the Norman invasion. Secondly, the onset of the Black Death devastated nucleated settlements such as walled Anglo-Norman towns, but had a significantly smaller impact in more sparsely populated Gaelic kingdoms. Lastly, and of most concern to the English crown, the gradual gaelicisation of the Normans meant that many of the most prominent Anglo-Norman families, who were meant to act as England's viceroys in Ireland, no longer followed English laws or customs.