ARCHAEOLOGISTS have uncovered the secret of a mysterious earth monument which has puzzled people for centuries.



The barely-visible bump on a Lancashire hill is the site of a lost castle.



The discovery has been hailed as one of the most important architectural finds in England for years.



Experts at Manchester University were stunned to discover the remains of a large 900-year-old castle, just a few miles north of Stalybridge.



The team had been commissioned to survey the entire borough of Tameside for historical artefacts. Although several ancient documents refer to a `castle' on windswept Buckton Moor few believed that such a structure existed.



Archaeologists had visited the moor on three previous occasions but those digs had yielded nothing. Although some raised earth mounds were visible, historians guessed they were the remains of a lowly earthwork fort, made by digging a ditch and building a simple wooden tower. It was not until earlier this year that they found the foundations of a 9ft deep wall and a huge gate tower, revealing that a football-pitched size castle capable of garrisoning up to 30 soldiers would have occupied the site.



Mike Nevell, director of the university's field archaeology centre, said: "The discovery of a high ranking castle in England is a tremendously rare event - and was definitely not what we were expecting.



"It's been an object of curiosity for a very long time - perhaps going all the way back to a reference in a 1359 survey carried out by Edward, the Black Prince, who had just acquired the lands. Then it was described as a ruined castle.



"Much of the stonework has been stolen and it's walls are overgrown with heather and peat which explains why it has been mistaken for an earthwork all this time."



Now historians are trying to discover who built and lived in the structure. Their best guess is that it was built by Earl of Chester, Ranulf the Second.



Controlling most of the counties in the north of England, the French-born aristocrat was one of the country's most powerful landlords.



Although he helped King Stephen conquer the warring Scots, the earl lived in a state of near constant conflict with the king and rival aristocrats, during a turbulent civil war.



He went on to survive a poisoning attempt by his arch-enemy William Peveril the Younger, which killed three of his men. He died at the age of 54, although the circumstances of his death are shrouded in mystery.



The university team, made up of professional archaeologists and local volunteers, will return for further excavations next year in an attempt to discover more about the castle.

In particular, they want to find out why it faced north rather than south where Chester's sworn enemy Peveril lived.