The series of magnificent 13th-century wall paintings was found inside a medieval chapel in Chester Castle, and experts believe that the early masterpieces may have been commissioned by King Henry III, who transformed the fortress into a royal palace in 1237.
The frescos are described as 'works of amazingly high quality' by the historian David Park, director of the Courtauld Institute's Conservation of Wall Painting Department.
If, as seems possible, they were commissioned by Henry III, they would be one of only a handful of medieval royal paintings known in Britain.
Their existence was forgotten about after the Reformation, or possibly the Civil War, when many of them were whitewashed over by Protestant zealots. Others were located so high up on the chapel walls that they escaped notice.
So far, conservators from the Courtauld Institute and English Heritage have succeeded in finding seven scenes. Painted in reds, whites, greens, blacks, blues and yellows, the scenes appear to depict miracles apocryphally attributed to the Virgin Mary: a thief who regularly prayed to Mary being saved from the gallows, a sinner's soul being snatched back from the Devil, a saint being resurrected to slay a pagan emperor. A fourth is believed to portray a miracle in which the Virgin Mary forced a bishop to reinstate a half-witted priest who had been relieved of his duties because he could only memorise one Mass. Luckily for him, it was one associated with the Virgin.
Other scenes depict the Virgin Mary embracing John the Baptist's mother Elizabeth prior to the birth of Christ, while another depicts the adoration of the infant Christ by the three kings.
Particularly well-preserved on the chapel's east wall is a bearded man wearing a conical wide-brimmed hat. His identity, however, is a mystery.
A large part of each scene has either not survived at all or survives in a faint state. But other parts, especially the heads, are in extremely good condition.
The newly discovered Chester frescos may have been the work of one of King Henry's leading artists - a monk called Master William of Westminster. It is perhaps significant that the angels in the Chester chapel bear an uncanny resemblance to some sculpted angels in Westminster Abbey.
Originally, the Chester chapel frescos probably covered about 100 square metres (320 square feet), of which around 16 square metres (51 square feet) is thought to survive, 25 per cent of it in superb condition. The works were painted on the chapel walls and on its beautiful ribbed Gothic ceiling.
The discovery - which is of international importance - involved careful scientific work. Six conservators have been gradually uncovering the newly discovered masterpieces over the summer. Each fragment is being carefully measured and drawn. Tiny samples of the frescos' pigment are being taken for analysis. Moisture levels within the paintings themselves will be regularly checked, and tests are continuously being undertaken to assess the best way to remove the whitewash which has covered some of the paintings for so long.