It’s been buried for over 400 years, missing in action deep below Edinburgh Castle’s cobbled wynds, but thanks to the sharp eye of Historic Scotland’s archaeologist, Peter Yeoman, another significant piece in this iconic attraction’s historical jigsaw has been discovered.

While excavating the area around where a new audio guide kiosk is scheduled to be erected (just inside the Castle’s portcullis gate), Peter and his team unearthed a finely carved stone window jamb reused in a drain. Peter immediately recognised the possibility that this might be the only fragment of the lost medieval Constable’s Tower that has ever been seen.

Peter explains: “I could see straight away that this was a fragment of a very fine glazed window probably of 15th or 16th century date. It must have been lying around as a piece of rubble to end up being built into this later drain. Putting two-and-two together, I realised that the only building it might have come from in this vicinity was the lost Constable’s Tower.

“Such a large window, at least five feet high, might have graced the Constable’s private apartments, from which he could have looked out, observing the coming and goings of the royal court in the nearby royal palace buildings. More warlike, smaller windows would have looked out to the town below.”

The Constable was the keeper of the castle for the king - a powerful and highly sought after position. The Constable’s Tower at Edinburgh Castle was built during the reign of Robert II (1371-90) as a new inner gate tower and was provided with a drawbridge in 1383. The Tower is recorded in drawings of the Castle which show little detail other than a large circular tower. It was destroyed in 1573 at the end of the ‘lang siege’ when a devastating fire brought the frontal defences (and the tower) crashing down.

Another important discovery made during the dig was the handle of a finely decorated bone knife which probably belonged to an 18th century red coat. The two week dig is now completed, although further analysis of the window and other discoveries is still underway.

The new audio guide kiosk forms part of a wider programme of improvements to ticketing and visitor reception at Edinburgh Castle, including the construction of a new ticket office which is currently underway. The new facilities are on track to open in 2008.

Barbara Smith, executive manager of Edinburgh Castle said: “Thanks to our archaeologist's nimble eye, another significant piece of Edinburgh Castle's complex history has been found and we are absolutely thrilled. Each discovery gives us a fascinating glimpse into the past, helping us to understand more fully the castle's role through the ages. It is an exciting find, proving that we are not even close to realising the full extent of buried treasure at Edinburgh Castle.”