The most detailed-ever map of Britain's genetic ancestry has revealed the influence of European migration over thousands of years.
High resolution DNA analysis identified 17 genetic clusters around the UK, each with a unique lineage to settlers from France, Germany or Scandinavia.
It found the Caucasian population of central and southern England is relatively homogeneous and can trace around 20% of its genetic heritage to the Anglo Saxon people who arrived in the country around 450AD, after the collapse of the Roman Empire.
But the study also shows that people who would consider themselves to have Celtic origin are in fact several distinct genetic groups - in many cases more similar to the English than they are to each other.
Researchers at the University of Oxford took DNA samples from more than 2,000 people who lived within 50 miles of their grandparents' place of birth. This meant the scientists were, in effect, able to look at the genetic make-up of different regions before the mass migrations of the 20th century.
They also took DNA samples from 6,000 people from around Europe to identify the origins of migrant groups.
Lead researcher Professor Peter Donnelly told Sky News: "One of the nice things about our study is that it reminds us that everyone in Britain is an immigrant.
"There was no-one in Britain 10-11,000 years ago. It is only a question of when people arrived."
According to results published in the science journal Nature:
:: Much of 'white British' DNA can be traced to people who colonised the island soon after the end of the Ice Age.
:: From the south coast to Yorkshire there is a distinct genetic pattern of the Angles - people who came from the southern Danish peninsula - and the Saxons, who came from North West Germany.
:: The populations of Cornwall and Devon are genetically distinct from each other, with a remarkable alignment with the county boundary.
:: There are other genetically distinct clusters on the English-Welsh borders, Pembrokeshire, North Wales, Cumbria, West Yorkshire, Northern Ireland and West Scotland and North East Scotland
:: Orkney is the only place in the UK with a significant genetic heritage from the Vikings, with 25% of the DNA originating from the Norse.
Dr Michael Dunn, Head of Genetics and Molecular Sciences at the Wellcome Trust, which funded the study, said: "These researchers have been able to use modern genetic techniques to provide answers to the centuries' old question: 'Where do we come from?'.
"Beyond the fascinating insights into our history, this information could prove very useful from a health perspective, as building a picture of population genetics at this scale may in future help us to design better genetic studies to investigate disease."