Isle of Anglesey in the context of "Holy Island, Anglesey"

The Norman invasion of Wales began shortly after the Norman conquest of England under William the Conqueror, who believed England to be his birthright. Initially (1067–1081), the invasion of Wales was not undertaken with the fervour and purpose of the invasion of England. However, a much stronger Norman invasion began in 1081 and by 1094 most of Wales was under the control of William's son and heir, the later King William II. The Welsh greatly disliked the "gratuitously cruel" Normans, and by 1101, had regained control of the greater part of their country under the long reign of King Gruffudd ap Cynan, who had been imprisoned by the Normans for twelve years before his escape.

In one incident, Gruffudd had some indirect help from King Magnus III of Norway (Magnus Barefoot) who attacked the Normans briefly off the Isle of Anglesey in northwest Wales near Ynys Seiriol, killing Hugh of Montgomery, 2nd Earl of Shrewsbury.

Gwynedd (Welsh: [ˈɡwɨnɛð]) is a county in the north-west of Wales. It borders Anglesey across the Menai Strait to the north, Conwy, Denbighshire, and Powys to the east, Ceredigion over the Dyfi estuary to the south, and the Irish Sea to the west. The city of Bangor is the largest settlement, and the administrative centre is Caernarfon. The preserved county of Gwynedd, which is used for ceremonial purposes, includes the Isle of Anglesey.

Gwynedd is the second largest county in Wales but sparsely populated, with an area of 979 square miles (2,540 km) and a population of 117,400. After Bangor (18,322), the largest settlements are Caernarfon (9,852), Bethesda (4,735), and Pwllheli (4,076). The county has the highest percentage of Welsh speakers in Wales, at 64.4%, and is considered a heartland of the language.

Holyhead (/ˌhəʊliˈhɛd, ˌhɒliˈhɛd/; Welsh: Caergybi pronounced [kɑːɨrˈɡəbi] , "Cybi's fort") is a historic port town, and is the largest town and a community in the county of the Isle of Anglesey, Wales. Holyhead is on Holy Island, bounded by the Irish Sea to the north, and is separated from Anglesey island by the narrow Cymyran Strait, having originally been connected to Anglesey via the Four Mile Bridge.

In the mid-19th century, Lord Stanley, a local philanthropist, funded the building of a larger causeway, known locally as "the Cobb"; it now carries the A5 and the railway line. The A55 dual carriageway runs parallel to the Cobb on a modern causeway.