HEREFORDSHIRE, England (AP) _ England's last great medieval castle opened Tuesday after undergoing a three-year project to preserve it as a romantic ruin before it collapsed.

Wigmore Castle, which was built to establish control over the Welsh frontier just after the Normans invaded England in 1066, dominates a wild and wind-swept hilltop in western England.

Once one of the richest and grandest of castles, it passed into royal ownership in the 15th century, but by 1530 was derelict and used only as a prison. It was finally abandoned in 1643 and has not been touched since.

Most of the surviving structure is believed to date back to the early 14th century, perhaps the castle's most romantic period, when it was lived in by Roger IV de Mortimer, the lieutenant in Wales for King Edward II.

Mortimer was known to have been the lover of Queen Isabella, and was implicated in the king's murder in 1327.

The site was in danger of collapse until English Heritage, the government agency responsible for the conservation of historic sites, carried out the $1.65 million project, which unlike most such projects did not excavate the site to reveal buried buildings.

``We decided to ... adopt an entirely new approach to its conservation and presentation. We would consolidate the ruins so that the castle could remain a romantic ruin forever,'' said Sir Jocelyn Stevens, chairman of English Heritage.

Much of the castle's past lies buried some 25 feet beneath the surface, he said _ ``a time-capsule and one of the most important archaeological sites in England, undisturbed.''