History of Killyleagh Castle
Taken from: "A tourist Guide to Killyleagh and District"
Killyleagh was settled in the 12th century by John de Courcy and fortifications were established on what is now the site of the castle. The subsequent history of Killyleagh is obscure until 1605 when Con O'Neill of Clandeboye owned large areas of North Down, including Killyleagh. However, suspected of treason, O'Neill was held prisoner in Carrickfergus Castle. His release was arranged by two Scots, Hugh Montgomerie and James Hamilton, who devised a plan to obtain a pardon for O'Neill in return for a division of his lands. Montgomerie took almost all of the Ards Peninsula and Hamilton the lands from Killyleagh to Bangor.
In 1622 James Hamilton was created Viscount Clandeboye and a map of Killyleagh in 1625 shows his castle as having a single tower on the south side of a residence. Hamilton's son was elevated in the peerage to become the Earl of Clanbrassil. He was closely allied to the Stuart Monarchy and in 1649 the castle was besieged, partly destroyed and conquered by Cromwellian forces. The Earl paid £9,435 for the return of the lands and castle but died in 1659, the title being taken by his son Henry at the age of twelve. Henry completed and education at Oxford and set about restoration of the castle in 1666. He added the North tower and either erected or restored the long fortified bawn in the front of the castle. It was Henry who provided and education for Hans Sloane, the son of the agent and receiver of taxes for the Earl. Hans Sloane's subsequent achievements were in science and medicine.
Henry Hamilton, the second Earl, married Lady Alice Moore, the daughter of the Earld of Drogheda and their only child died in infancy. This childless state had complex consequences for Killyleagh Castle. Lady Alice discovered the 1st Earl had stated in his will that should Henry die without issue the properties and lands should be divided between five cousins. Lady Alice destroyed this will and had her husband make a will of his own bequeathing the estates to her. Within a year of making this will Henry was poisoned in Dublin. Lady Alice had little time to enjoy her bequest as she dies two years later, leaving the estate to her brother. The cousins, however, were aware of the provisions of the destroyed will and pressed their case as the rightful owners of the estates. This case was terminated after some 20 years upon the discovery, in the castle, of a valid copy of the original will. Alas, by this time all the cousins were dead. The last to die, James Hamilton, being confident of a final settlement to his favour, bequeathed the estate to be divided with one half going to his own daughter Anne Hamilton and the other half to his nephews Gawn and William Hamilton. The probate court in 1697 followed his wishes but with extraordinary consequences. The castle was divided; Gawn and William received the main house and twin towers, whereas Anne received the large fortified bawn and the gates. This judgement left Gawn and William unable to enter their own castle and they had to create a new entrance on the north side.
Anne married Hans Stevenson and her part of the property passed to their son James. James provided the Church of Ireland rectory in 1733 (Church Hill House). The estates and bawn passed to Dorca Stevenson, daughter of James and she married John Blackwood, bringing the Hamilton estate of Clandeboye into the Blackwood family, their title eventually becoming Lord Dufferin and Ava. On Gawn's side the castle passes through successive generations of Hamiltons to Archibald Rowan Hamilton who, in 1849, commenced a substantial renovation of the castle under the direction of the great architect Laynon (also responsible for the main building at Queen's University). The two families remained divided, as did the castle, until 1860 when Lord Dufferin gave the bawn and gate house to the Hamiltons and even commissioned a replacement gate house to better match the main castle. In return for this unification of the castle, the Hamiltons gave a set of silver spurs and a golden rose, each on alternate years.
The castle and estates have thus been fought over in courts and in actual battle. They have been bought and sold and used as payment for pardons. The castle has been knocked down and rebuilt, extended, altered. Split and reunited. It is still occupied by the Hamilton family and is their private residence. However, of late, it is invaded annually by thousands who attend outdoor concerts in the bawn 
