Medieval sources

Domesday Book
(originally King’s Roll or Winchester Roll) is a land register of England that records the results of nationwide investigations in the 11th century in Latin. The book's unusual name became common in the century after the survey. He was referring to the fact that the real estate relationships recorded in the Domesday Book were considered legally "final".

Threatened by an invasion, King Wilhelm I (the Conqueror) ordered at Christmas 1085 that his own and taxable property of his subjects be systematically recorded. From January 1086, his emissaries combed the country as planned and determined not only the properties and their owners, but also the number of male residents. Domesday here has the meaning of final, i.e. H. later the ownership stipulated in the Domesday Book should no longer be contestable.

The background to the measure was the centuries-old property structure in England, which was largely based on customary law: peasants and aristocrats had land and rights that were not documented in writing, as only a few people could read and write, and through gifts, sales and inheritance etc. the lands were severely fragmented. Thus, prior to the Domesday Book, the Norman conquerors had no reliable information that could serve as a basis for calculating expected tax revenues. Since Wilhelm almost constantly waged war against internal and external enemies, he was dependent on being able to reliably estimate the expected tax revenues and the number of the population conscripted. The creation of the book marked the first census in England and an important step on the way to centralizing power away from the local nobles and towards the royal court.

The book, which was written in two volumes, was not continued after 1090, but it presents the circumstances of the period considered in great detail. From then on, any legitimation of land ownership arose from this register, which can still be used today. Since Wilhelm II of England, the distribution of the army burden according to so-called knightly fiefs and the precise formation of burdens and legal relationships of the English feudal system have been regulated with the help of the Domesday Book. In the course of only 50 years the English Treasury (Exchequer) was created, which worked on the basis of the Domesday Book. Despite verifiable gaps, the work gives indications of the country's population at that time, which must have been around 2 million.

Half of the land that was given as a secular fiefdom in England under William the Conqueror belonged to only eleven men who almost all of William's blood relatives.

Annals of Tigernach
(Irish: Annála Thighearnaigh) are among the most important medieval chronicles of Ireland. They are largely written in Irish with some Latin entries. The chronicle covers the periods from 807 BC. BC to 360 (as a copy of the chronicles of Eusebius of Caesarea) and from 489 to 1178 with gaps between 767 and 973 and between 1004 and 1017.

According to the English historian Kathleen Hughes' analysis, there are great similarities between the Annals of Ulster and the Annals of Tigernach in the period from 489 to 766, so that it seems reasonable to suggest a common origin. Hughes assumes that these are the non-preserved annals of Iona.

The surviving manuscripts are divided into five fragments, of which the first fragment was created in the 12th century and the other fragments date from the 14th century. The first fragment covers the period from 807 BC. Chr. to 160 from. The second fragment covers the years 322 BC to 360. The remaining three fragments extend over the years 489 to 766, 973 to 1003 and 1018 to 1178.

All fragments come from the collection of the Sligo historian Dubhaltach Mac Fhirbhisigh. His collection went to Robert Ware, who sold it in 1686 to the Earl of Clarendon, who bequeathed it to Duke of Chandos, after whose death it was auctioned in 1746. Substantial parts of this collection including all surviving manuscripts of the Annals of Tigernach came into the possession of Richard Rawlinson in this auction, who passed them on to Oxford University, where they have since been kept in the Bodleian Library.

The Annals of Ulster
(Irish: Annála Uladh) are among the most important medieval historical works of Ireland. They are largely written in Irish with very few Latin entries. They cover the period from 431 to 1541. They were compiled in the 16th century.

There are four surviving manuscripts:
-   The manuscript from the library of Trinity College in Dublin was compiled in its entries up to the year 1489 by the copyist Ruaidhrí Ó Luinín. Later entries were made by other authors. The entries for 1102 to 1108, 1115.4-1162.3 and 1374 to 1378 are missing.
-   The manuscript from the Bodleian Library of Oxford University includes entries up to 952 (compiled by Ruaidhrí Ó Casaide), the following entries up to 1507 by Ruaidhri Ó Luinín and a few other copyists unidentified with the exception of Matha Ó Luinín. The entries for 1131.3-1155 and 1307 to 1315 are missing.
-   The British Library in London has an English translation of the Irish text for entries 431 to 1132.1, 1156 to 1307 and 1486 to 1504. This text contains some entries that have not survived in the Irish original.
-   Another manuscript in the British Library in London is a translation of the Irish text into Latin, covering the period from 1200 to 1296. Material from other sources was also adopted.