Richard de Clare, 2nd Earl of Pembroke in the context of "Diarmait mac Murchada"

Cambro-Normans (Latin: Cambria; "Wales", Welsh: Normaniaid Cymreig; Norman: Nouormands Galles) were Normans who settled in southern Wales and the Welsh Marches after the Norman invasion of Wales. Cambro-Norman knights were also the leading force in the Cambro-Norman invasion of Ireland, led by Richard de Clare, 2nd Earl of Pembroke in 1170.

Laudabiliter was a bull issued in 1155 by Pope Adrian IV, the only Englishman to have served in that office. Existence of the bull has been disputed by scholars over the centuries; no copy is extant but scholars cite the many references to it as early as the 13th century to support the validity of its existence. The bull grants the right to the Angevin King Henry II of England to invade and govern Ireland and to enforce the Gregorian Reforms on the semi-autonomous Christian Church in Ireland. Richard de Clare ("Strongbow") and the other leaders of the Anglo-Norman invasion of Ireland (1169–1171) claimed that Laudabiliter authorised the invasion. These Cambro-Norman knights were retained by Diarmait Mac Murchada, the deposed King of Leinster, as an ally in his fight with the High King of Ireland, Ruaidrí Ua Conchobair.

Successive kings of England, from Henry II (1171) until Henry VIII (1542), used the title Lord of Ireland and claimed that it had been conferred by Adrian's successor, Pope Alexander III (c. 1100/1105 – 1181).

Sigillography, also known by its Greek-derived name, sphragistics, is the scholarly discipline that studies the wax, lead, clay, and other seals used to authenticate archival documents. It investigates not only aspects of the artistic design and production of seals (both matrices and impressions), but also considers the legal, administrative and social contexts in which they were used. It has links to diplomatics, heraldry, social history, and the history of art, and is regarded as one of the auxiliary sciences of history. A student of seals is known as a sigillographer.

Osraige (Old Irish) or Osraighe (Classical Irish), Osraí (Modern Irish), anglicized as Ossory, was a medieval Irish kingdom comprising what is now County Kilkenny, western County Laois and parts of eastern County Tipperary, corresponding to the Diocese of Ossory. The home of the Osraige people, it existed from around the first century until the Norman invasion of Ireland in the 12th century. It was ruled by the Dál Birn dynasty, whose medieval descendants assumed the surname Mac Giolla Phádraig.

According to tradition, Osraige was founded by Óengus Osrithe in the 1st century and was originally within the province of Leinster. In the 5th century, the Corcu Loígde of Munster displaced the Dál Birn and brought Osraige under Munster's direct control. The Dál Birn returned to power in the 7th century, though Osraige remained nominally part of Munster until 859, when it achieved formal independence under the powerful king Cerball mac Dúnlainge. Osraige's rulers remained major players in Irish politics for the next three centuries, though they never vied for the High Kingship. In the early 12th century, dynastic infighting fragmented the kingdom, and it was re-adjoined to Leinster. The Normans under Strongbow invaded Ireland beginning in 1169, and most of Osraige collapsed under pressure from Norman leader William Marshal. The northern part of the kingdom, eventually known as Upper Ossory, survived intact under the hereditary lordship until the reign of King Henry VIII of England, when it was formally incorporated as a barony of the same name.

William Marshal, 1st Earl of Pembroke (1146 or 1147 – 14 May 1219), also called William the Marshal (Norman French: Williame li Mareschal, French: Guillaume le Maréchal), was an Anglo-Norman soldier and statesman during High Medieval England who served five English kings—Henry II and his son and co-ruler Young Henry, Richard I, John, and Henry III—as a royal adviser and agent and as a warrior of outstanding prowess.

Knighted in 1166, William spent his younger years as a successful competitor in military tournaments; 13th century chronicler Stephen Langton eulogises him as the "best knight that ever lived." In 1189, he became earl of Pembroke through his marriage to Isabel de Clare, whose parents were Aoife MacMurrough and Richard de Clare, 2nd Earl of Pembroke. The title of earl was not officially granted until 1199 and is considered to be the second creation of the Pembroke earldom. In 1216 upon the death of King John, William was appointed protector for John's nine-year-old Henry III and rector regis et regni (Latin for "governor of the king and of the kingdom"). Just before his death, William fulfilled a promise he said he made in his youth while on crusade by taking vows as a Knight Templar, and was buried in the Temple Church in London.

Christ Church Cathedral, more formally The Cathedral of the Holy Trinity (Irish: Ardeaglais Theampall Chríost), is the cathedral of the United Dioceses of Dublin and Glendalough and the cathedral of the ecclesiastical province of the United Provinces of Dublin and Cashel in the (Anglican) Church of Ireland. It is situated in Dublin, Ireland, and is the elder of the capital city's two medieval cathedrals, the other being St Patrick's Cathedral.

The cathedral was founded in the early 11th century under the Viking king Sitric Silkenbeard. It was rebuilt in stone in the late 12th century under the Norman potentate Strongbow, and considerably enlarged in the early 13th century, using Somerset stones and craftsmen. A partial collapse in the 16th century left it in poor shape and the building was extensively renovated and rebuilt in the late 19th century, giving it the form it has today, including the tower, flying buttresses, and distinctive covered footbridge.