Stonehenge is one of the most enigmatic and fascinating historical sites that Britain has to offer, largely because historians have little idea what the huge stone monoliths were for, or how they got there. There's no end of theories, but none of them so far have been conclusive. Recent revolutionary research has just been undertaken which, over the course of four years, has yielded some fascinating insights into the site. Drawing on this new data, archaeologists might finally be able to put to bed some of its mysteries. This two-part programme reveals the project's findings.