When tracing our British ancestry, unless we descend from Royalty or Normans, in the past we have not been able to determine the origins of our British immigrants. Of British immigrants, i.e. our ancestors who came over from the European Continent and settled in the British Isles over 1000 years ago, apart from statements by the Venerable Bede, basically no specific details were recorded on either side of the English Channel. Those stuck on more modern immigration problems have it easy compared to this type of research. Recent advances in DNA studies and comparisons between human populations have enabled us to interpret our deeper past.
Historical Recap of Britain's Recorded Conquerors
The first conquerors of Britain were the Celts. They began arriving in the first millennium B.C. from across the English Channel in what is now France. They overpowered the previous inhabitants. During the century preceding and following the lifetime of Jesus Christ, the Romans conquered Britain. They referred to the native inhabitants - the Celts - as the British and ruled during the first few centuries A.D. By the fifth and sixth centuries A.D., the Roman Empire had lost much of its power, and Germanic tribes, such as the Angles and Saxons invaded the islands. They were followed in the ninth and tenth centuries by Scandinavian Viking raids and conquests. All of these events preceded William the Conqueror's Invasion of 1066. Each of the different peoples settled in specific regions of the British Isles, although there was intermixing. Oxford's Dr Bryan Sykes's research indicates that "In the modern-day male population of the British Isles, three ancestral tribal groups account for the origins of 95% of Y-chromosomes: the Celts, the Anglo-Saxons/Danish Vikings and the Norse Vikings."
Incompleteness of the Historical Record
Basically, no records survive to document the mass of common people living in the British Isles before the Norman Conquest. By identifying where in England, Ireland, Scotland or Wales our ancestors lived during the Middle Ages, we have hints as to their immigrant origins, but nothing substantial. You can read more about the geographical distribution of these distinct peoples, which can be heard today in regional dialects and place-names, and view explanatory maps at http://www.great-britain.co.uk/history/ang-sax.htm.
The Role of DNA
DNA steps in to provide a solution to these record gaps and helps us understand the European origins of some of our British ancestors. Oxford Ancestors, run by Dr Bryan Sykes of the University of Oxford, the discoverer of DNA's value to genealogy, offers a simple test to reveal which of three conquering peoples your DNA floated around in 1500 years ago. Their product "Tribes of Britain™," promises to reveal what category of conqueror's DNA descended down through the millennia in your paternal lineage to you.
Read more about it at Oxford Ancestors.