Work begins to uncover secrets of Silbury Hill By Richard Savill Last Updated: 2:26am BST 12/05/2007 Work began yesterday to save an ancient landmark in Wiltshire from collapsing. Silbury Hill, which at 130 feet high is the largest prehistoric man-made construction in Europe, continues to mystify archaeologists. English Heritage is to spend £600,000 this summer trying to preserve the mound. Specialist engineers will enter the mound through a tunnel which was dug in 1968 by a team led by the archaeologist, Prof Richard Atkinson. That tunnel was the last of three made over two centuries by archaeologists. The original purpose...