Book excerpt: In 54BC Julius Caesar invaded Britain. His account of that invasion was written up by a number of historians and in it he described various British tribes by their different characteristics. Some were tall and warrior like, others were swarthy and less threatening. Each tribe lived in its own particular area. Some fought with each other; others believed in allegiances. All were subsumed by Rome.Always fascinated by the genealogy of peoples, Bryan Sykes began to wonder what might have become of these tribes. Did they simply disappear in a genetic pool of Roman DNA and subsequently Saxon and Viking and Norman, or did they survive intact? In a major and unique DNA research programme, Bryan Sykes and his team at Oxford University set out to test over 10,000 DNA samples from across the UK with the specific aim of answering this very question: what is the DNA make-up of the UK? Did the Vikings rape and pillage their way throughout Britain? If they did, this would show up in today's DNA samples. And what of the Normans, the Saxons or the Celts? Is modern-day Britain a cocktail of DNA reflecting the history of this country or did the invaders mostly keep to themselves, leaving the original inhabitants free to marry and produce among themselves?As his findings came in, Bryan Sykes discovered that the evidence revealed a completely different and potentially shocking story. The Blood of the Isles will reveal the nature of Britain's genetic make-up and what this says about Britain today. It is a gripping story that will fascinate and surprise with its dramatic conclusions.