HISTORIANS are digging deep in the hope of uncovering vital clues into the very earliest days of what would one day become heavy industry.

A metre-square trench at Rievaulx Abbey, near Helmsley, North Yorkshire, could shed new light on the ancient monks' early efforts with iron.

To mark National Archaeology Day, on Sunday, English Heritage has granted permission to a team from Bradford University to probe inside the ancient walls of the monk's refectory building.

They are looking for evidence to fuel their theory that it was once used to store vast amounts of charcoal, needed to feed a blast furnace at Rievaulx built after Henry VIII evicted the Cistercian brothers.

Jane Wheeler and Dr Jerry McDonnell were yesterday preparing for the dig - the first at Rievaulx in 80 years - by doing a geo-physics survey in the refectory.

They believe that before Henry VIII's intervention, monks were on the verge of developing blast furnace technology, which could have sparked a mini-industrial revolution in this tranquil corner of North Yorkshire.

However, the story did not end in the mid-16th Century. Records show that iron-making continued at Rievaulx until at least 1650 and that a blast furnace was indeed operating by 1570.

Storing the vast amounts of charcoal needed would have been a major headache, according to Dr McDonnell.

"More than a tonne of fuel would be needed every day so we are talking about a substantial volume of material," he said. "Our hunch is that the monastic refectory could have been used. We know the building survived dissolution reasonably intact and was marked down on the Ordnance Survey map of 1856. We will be probing the surface for bits of charcoal and other telltale debris."

Two years ago, English Heritage and Bradford University built a working clay furnace, which produced iron at the site for the first time in 450 years.