Orkney — seven miles off the coast of Scotland, and cut off by the tumultuous Pentland Firth, the fastest-flowing tidal race in Europe is often viewed as being remote. However it is one of the treasure troves of archaeology in Britain, and recent discoveries there are turning the Stone Age map of Britain upside down. Rather than an outpost at the edge of the world, recent finds suggest an extraordinary theory — that Orkney was the cultural capital of our ancient world and the origin of the stone circle cult which culminated in Stonehenge. In the second of this three-part series, Neil Oliver, Chris Packham, Andy Torbet and Dr Shini Somara join hundreds of archaeologists from around the world who have gathered there to investigate at one of Europe's biggest digs. Andy and some local seafaring volunteers build a boat made of just willow and cow hide and set out to cross the dangerous Pentland Firth as the ancient Orcadians would have done. Neil investigates the extraordinary discovery of some human bones, Chris goes in search of whales and Shini uncovers the powers of the tides.