Niall is reputed to have captured and enslaved the teenage Magnus Succetus - who later returned to preach Christianity as Patricius - in a raid on the Cumbrian or Welsh coast.

The descendants of Niall's son Fiacha (Fiachu Fiachrach) were collectively known as Cenel Fhiachaigh, of the southern Ui Neill (later anglicised as Kenaleagh and Kindalane).

[citation needed] The Geoghegan family were major landholders in south Westmeath and maintained a peaceful co-existence with the Tudor reconquest through a process known as "surrender and regrant".

As the reign of the Stuarts led to the English Civil War (1642–1651), and the events of 1641 to the Cromwellian invasion of Ireland, the family suffered losses after the Down Survey and the ensuing plantations.

They lost a considerable portion their estates to Gustavus Lambart (later created Earl of Cavan) through confiscation even prior to the final publication of the Down Survey.

[citation needed] The Restoration resettlement acts of the late 17th century favoured the retention of land by some of the recently ensconced Cromwellian "adventurers" and "undertakers" and some to their traditional owners.

It did not help the case for a greater degree restoration of Geoghegan land that the chieftain Bryan and many of his allies of the "Irish of Meath" coalition refused to sign the mandatory pledges and undertakings of fealty to the new regime of William and Mary, to parliament and to the established church.