ONE of the biggest prehistoric hillforts ever found in Britain has been unearthed by archaeologists at a North Yorkshire beauty spot, English Heritage said today.

The 40-acre monument at Sutton Bank, near Thirsk, is thought to have been surrounded by a 1.3 mile-long rampart, topped with a walkway, and to date back to about 400BC.

The fort, which was built against a steep escarpment giving it views for miles across the Vale of York, was discovered by English Heritage archaeologists who spent this summer surveying the site.

Field investigator Alastair Oswald said there had been suspicions of a prehistoric hill fort at the location since the last century when a small number of Iron Age earthworks were discovered.

But Mr Oswald said the breathtaking array of ditches, humps and bank was much more extensive than anyone had thought.

He said: "Hillforts 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 Parisi tribes."

Updated: 15:22 Thursday, November 01, 2001