Television programmes exploit archaeology, often very well, but rarely make an active contribution to scholarship. But this happened last summer, however, when the Big Royal Dig at Windsor Castle, carried out by the Channel 4 Time Team, uncovered the first solid evidence for Edward III’s Round Table of 1344.

Not to be confused with King Arthur’s Round Table (the magnificent piece of medieval English carpentry which hangs on the wall of Winchester Castle, made for Edward’s grandfather, Edward I), the Windsor construction was a stone building some two hundred feet in diameter. It stood for less than 20 years, and no sign of it had been seen for more than six centuries. Some doubted its very existence.

“Having harboured an archaeological fantasy about digging up Windsor Castle to find Edward III’s fantasy building, the House of the Round Table, itself the product of an Arthurian fantasy court life, we then found its remains,” said Julian Munby, one of the authors of a new book, produced nine months after Time Team’s revelation. “We further discovered a whole literary fantasy relating to round-table buildings. I think no one quite believed what the sources told us, and now we can do so with confidence.”

Richard Barber, another of the authors, said: “Edward III proposed to found an order of three hundred knights to recreate the Round Table as it had existed in Arthur’s time. We have to remember that most of his contemporaries regarded King Arthur and his Knights of the Round Table as historical reality.”

Edward announced his idea at a solemn ceremony, wearing the Great Crown and accompanied by his officers of state, in January 1344, after a flamboyant display which was intended to garner political support. Edward’s military adventures, apart from the naval victory at Sluys in 1340, had not so far been very successful.

Adam of Murimuth, a canon of St Paul’s, wrote in his Continuatio Chronicarum of the jousting in which Edward III and 19 other knights fought for three days. At the end, Adam says, the King held “a great feast at which he announced the foundation of his Round Table, and took the oaths of certain lords, barons and knights who wished to be members. He afterwards commanded that a most noble building should be built. . . and instructed masons, carpenters and other workmen. . . not sparing either labour or expense.”

The building accounts, as Munby details, have long made it impossible to dismiss the scheme as unfulfilled: from February until November of 1344 substantial sums were laid out on labour – more than £300, some 60 per cent of the total – and materials, which cost £125; the rest went on transporting the stone from regional quarries near Oxford, Maidstone and Milton Keynes, and bringing imported Caen and Yorkshire stone from London yards. Strengthening of the castle bridges to bear the weight provided a vital clue to Sir William St John Hope in 1913 that the Round Table building had been located in the Upper Ward of Windsor Castle, which is where it was found.

The archaeological remains, detected initially by remote sensing and then confirmed by one of Time Team’s trenches just outside the Queen’s private apartments, consisted only of an arc of robber trench, where the walls had long ago been removed for reuse elsewhere, and an area of floor surface.

The Winchester Round Table shows the existing popularity of Arthurian romance, and Barber believes that it was essentially a theatrical prop. “The Windsor Round Table is a much grander project altogether,” Barber said.

“What we have tried to do is to take the archaeological discovery and work out from this the resouces employed, the architecture, and the cultural and political context.”

It was politics that made Edward’s grand idea redundant: in 1346 his great victory at Crécy brought in plunder, anchored the support of his nobles, and established his warrior reputation. He no longer needed to curry favour by bringing in so many knights, and in 1348 he established the much more exclusive Order of the Garter, also based at Windsor.

Within 15 years the Round Table building, probably never finished and possibly never used, had been demolished.

Edward III's Round Table at Windsor, Boydell & Brewer, ISBN 978-1-84383-313-0.