THE BBC is about to re-screen an archive TV film that has been used to investigate why a hole appeared at the top of ancient Silbury Hill.

In 1968, the BBC's Chronicle programme, presented by Magnus Magnusson, recorded the last archaeological investigation into the centre of Western Europe's largest artificial prehistoric mound.

The dig was led by Professor Richard Atkinson who was following the line of an earlier tunnel dug in 1849 by Dean John Merewether.

The moment when the mining engineer working with Atkinson, Dr John Taylor, broke into the Merewether tunnel and crawled down the unsupported 19th century shaft to the centre of the mound, was captured by the Chronicle programme.

Recently, archaeologists from English Heritage have been using BBC film and the latest seismic technology to investigate why the ancient mound collapsed twice in May and December 2000.

The hole has since been closed with blocks of polystyrene and a layer of chalk.

Magnus Magnusson narrates The Hill with a Hole, which has been produced by BBC West for Home Ground, a series showcasing some of the best documentaries made by the BBC's Nations and Regions.

The Hill with the Hole will be shown on BBC 2 at 7.30pm on Thursday.