Nicholas Bagenal appears to have come to Ireland after being implicated in a murder. After serving for a period of time as a mercenary soldier for the O'Neills, he received a general pardon in 1543. He entered the service of the English Crown and in 1547 he was appointed Marshall of the Army in Ireland. In 1550 was given a lease "of the college or house of Newry".
Nicholas Bagenal managed to maintain control of his lands in spite of incursions by Shane O'Neill. He was succeeded in 1590 by his son Henry who was later killed when fighting Hugh O'Neill at the Battle of Yellowford in 1598. Ironically Henry's sister, Mabel, had eloped with and married Hugh O'Neill in 1591.
Bagenal has been described as living in the Abbot's House, which was part of the Cistercian Abbey but he appears to have demolished it and built his own fortified house in the surrounding environs. Bagenal's "New Castel" is prominent in the earliest known map of Newry, which depicts the layout of the late 16th century town.
The Bagenal family line came to an end in 1712, and the estate was
divided between distant relatives Edward Bayley, who received land
in Co. Louth, and Robert Needham, who received the lands on counties
Down and Armagh, including Newry. In the 18th century, the
Needhams leased Bagenal's Castle to a merchant and they established
their principal residence at Mourne Park, near Kilkeel.
The map of Newry circa 1570, shows the town divided into three parts,
two of which were fortified, probably with an earthen bank and
ditch. In the area marked as ‘The Towne of The Newrye’ Bagenal’s
Castle is identified as ‘The New Castell’ © Crown Copyright.