FOR generations, the steep escarpment of Sutton Bank has been a renowned beauty spot, with its breath-taking views across miles of the Vale of York.

But new research using the most up-to-date technology has revealed its importance pre-dates the tourist industry by thousands of years.

For just above the White Horse of Kilburn, archaeologists have discovered the remains of one of the largest Iron Age hill forts in the country.

The spectacular 40-acre site, on the western edge of the North York Moors, is believed to date back to at least 400BC. It may have marked the border between two warring tribes.

Using global positioning technology and old-fashioned leg-work, archaeologists from English Heritage have discovered that the fort was enclosed by a two-metre deep trench and a four-metre high box rampart.

That was fronted by a timber palisade and topped by a defended walkway that has now been traced to a distance of 1.3 miles.

Only two entrances to the complex were detected, which would have added to the fort's impregnability.

Suspicions that a hill fort existed date back to 1853, when the Ordnance Survey mapped a short stretch of tell-tale Iron Age earth works.

Later, archaeologists failed to follow up the findings, confusing them with nearby medieval boundary ditches.

But in the wake of environmental work by the National Park Authority, English Heritage investigated the mystery further and over the summer a team carried out a meticulous survey of the area around Roulston Scar and the White Horse.

They found a series of ancient ditches, banks, humps, and other features that extended much further than was previously thought.

The area embraces much of the present-day airfield of the Yorkshire Gliding Club and in places some stretches of the defences survive to a height of almost three metres.

Field investigator Alastair Oswald said: "Hill forts are uncommon in Yorkshire, so we were obviously shocked to discover such a huge complex.

"It's possible the fort was constructed by the Brigantes or the Parisi tribes, perhaps more as a statement of power than a defensive bastion."

He said: "We didn't find much evidence of settlement within its boundaries, but it may have been a temporary refuge in times of trouble or a giant corral for livestock.

"What is for certain is that such a large fort would have taken a vast amount of timber and labour to build - which poses many more intriguing questions."

Because of the discovery, the area's Scheduled Ancient Monument designation will now have to be amended.

The National Park Authority is also deciding how to present the prehistoric monument to the thousands of walkers who pass through, on the Cleveland Way.