STARTLING new evidence has been unearthed which has shed fresh light on the glory days of one of the region's great monastic ruins.

Byland Abbey, near Coxwold in North Yorkshire, was once one of the largest Cistercian monasteries in England and even during its medieval heyday was described as one of the "shining lights of the north."

But the new research indicates it was probably more spectacular than experts previously thought.

The abbey was settled by monks in 1177 on what had been an insect-infested swamp. They drained the land and built the largest monastic church in England at the time - but the abbey's true scale may have been even greater than previously thought.

And for a while it may even have eclipsed North Yorkshire's two other great monasteries, at Rievaulx and Fountains.

Archaeologists with GPS equipment have been surveying the fields around the ruin, plotting humps and bumps in the ground that have puzzled historians.

Much of the area was believed to be under water during the monastic period, a mixture of lakes, fish ponds and bogs, with the abbey itself perched on an island of firm ground created by the monks.

But now extensive earthwork evidence of major monastic buildings has been discovered, linked together by causeways - some of which were previously mistaken for dams.

English Heritage senior archaeological investigator Al Oswald said: "It is not just that we are finding evidence of buildings where we thought there was water, but that these were major structures, laid out in a geometrical pattern.

"We know Byland's monks were gifted engineers and toiled for 30 years to drain the land, but if anything we may have underestimated their skills.

"Using rudimentary equipment, muscle and not a little faith, they drained a much larger area than we had thought. The abbey must have resembled a small town in its scale, making it one of the great feats of monastic engineering."

As part of the investigation researchers also plan to carry out a full search of literature, maps and illustrations, before the results are eventually used to re-write Byland Abbey's guidebook.

Visitor operations manager John Lax said: "It's dangerous to think that the definitive history has been written about any historic site.

"This latest research work at Byland is revealing the full scale of the monks' achievement in building this magnificent place, which even after 850 years stands firm on the ground they laboured to reclaim."