CHANNEL | BBC 2

FIRST BROADCAST | 27 July 1968

DURATION | 39 minutes 12 seconds

"Silbury is one of the largest prehistoric earthworks in Europe, possibly dating to 2400BC. In this programme, originally broadcast live, Magnus Magnusson meets the archaeologists who have uncovered a tunnel that leads into the heart of the mound."

More here - http://www.bbc.co.uk/archive/chronicle/8607.shtml