Carrickfergus Castle

Carrickfergus castle was built by the Anglo-Norman knight John de Courcy around 1177 AD after he conquered eastern Ulster. Becoming very powerful and having such an important position as Carrickfergus, King John sent another Anglo - Norman knight Hugh de Lacy to defeat de Courcy in 1204 and made de Lacy the Earl of Ulster.
In 1210 de Lacy fell out of favour with King John and so John with the aid of de Courcy defeated de Lacy . John stayed at Carrickfergus in July of that year as that was his strongest castle.

The king set up a constable named de Serlane to fortify the castle but that did not help in 1227 when de Lacy returned as the Earl of Ulster and took the castle again. John de Courcy, Hugh de Lacy and King John are the three who built and shaped the castle.