William the Conqueror (began to reign 1066, d. 1087, reigned 21 yrs.) divided his conquered lands into 700 baronies or great fiefs. These were the lands that did not belong to the church, and were not already reserved for himself. He bestowed these baronies on his family, particular friends, or those who had distinguished themselves in his service. These baronies were subdivided into 60,215 knights' fee. [We would consider "rent"!] No Saxons or Welsh had any of these first fiefs, and only a few Saxons were allowed (elevated enough) to obtain any of the later. This explains why most of the English genealogy books begin their lineage with the Norman conquest. An abstract of English printed peerage, by Richard Sims (1856), reports that out of 249 "nobleman", only 35 laid claim to have traced their descent beyond the Conquest. (14%) The Welsh are not even in the picture! Of course, Welsh documents were not considered to be legitimate records of the realm.
There were other records that had been kept before the Normans arrived. Monastic records head the list, and are the most ancient records known to exist. They (religious houses) needed to keep records of their secular estates. Many of these records were destroyed during the reign of Henry VIII. [Religious houses were considered abbies, priories, and cathedrals.] These monastic records have been divided into: 1) Chartularies, 2) Leiger-Books, 3) Registers, 4) Obituaries, 5) Necrologies, 6) Calendars, and 7) Chronicles. [seven, a good religious number] These are given in great detail in one of the first genealogial text titled "Sims's Manual For The Genealogist and Antiquary", by Richard Sims (of the British Museum), John Russell Smith, London, 1856. A copy I have in my hand as I write this post!
It was the Celtic church writers that were the first to record the family trees of the Welsh! [see post called Eliseg Pillar under blog on Welsh genealogy] Writing in Latin, these records began 500 years before the Normans arrived to our island. Who would have guest.