Norman Invasion - Ireland
The background to the Norman invasion of Ireland is a long story, well laid out at http://www.teachnet.ie/mmorrin/norman/why.htm. The history of this area, however, with Drogheda barely a mile away we think, extends back millenia. Read this venerable tourist-writing book, "In Search of Ireland" by H. V. Morton, see review at http://christine-breen-williams.suite101.com/in-search-of-ireland-hvmorton-a178724, from 1930, and later reprintings. Drogheda and Carrickfergus see pages 270ff.
The Normans, after their invasion of England in 1066 with William the Conqueror, invaded Ulster (the north of Ireland) with a permission, then did not leave. The Welsh Norman Lord, Richard de Clare, known as Strongbow, acted to help restore the Leinster King to his throne, and in exchange for a marriage to the King's daughter, and other benefits of inheritance as to the throne itself. No wonder he came, with army. He also had permission of the English King Henry II, who had been asked for help by the deposed Leinster king and then turned to Strongbow to do it. A more complex account of Strongbow - worth reading - is at http://www.houseofnames.com/xq/asp/sId./kbId.129/qx/knowledgebase.htm/. For a quick review, see everyman's starting point for perspectives, at http://www.en.wikipedia.org/wiki/Richard_de_Clare,_2nd_Earl_of_Pembroke.
The town was walled by the 1300's. The fine castle on the water is also called Carrickfergus. The first fortification on the site was apparently 150 years BC, see http://www.libraryireland.com/Belfast-History/Carrickfergus.php. Here is a fair use thumbnail of the site now, from http://www.photos.igougo.com/images/p239247.
Find its history at http://www.culturenorthernireland.org/article.aspx?art_id=931
That castle was begun long before, in 1180, as a protection to Belfast Lough.
Ireland and Europe show vast educational advantages compared to our isolation from so much history. Schoolchildren here learn history from their backyards. At this castle, for example, there are staging sets, exhibits, classrooms, mannequins, scenes, all showing Carrickfergus in 1180 and to now. See http://www.geographia.com/northern-ireland/ukiant03.htm.
Turn the corner around from one of the staircases, and find the king, crown askew, on the loo, drawers crumpled at his feet, chin on hand, and school kids seeing it for the first time, giggling and pointing. Great fun.
Carrickfergus is huge, like the photo of what now know is Caernarfon in Wales,* see note.
Update January 2009 - We had originally posted this picture, but later found it is not Carrickfergus,but Caernarfon, that we also visited. See comment. My son and I are sure we a "Carrickfergus" but this was before memory cards.
Caernarfon Castle, Wales - First believed to be Carrickfergus - bad record-keeping
There are similarities between Carrickfergus and Caernarfon, but this one turns out to be Castle Caernarfon in Wales, where the Prince of Wales is customarily crowned. See Ireland Road Ways, Caernarfon Castle and the Prince of Wales.
All information is a matter of pooling and checking. Vet it all. Thanks. The comment that first alerted us includes a picture of Carrickfergus so check it there.