Hidden Depths - The Secret Tunnel Under Edinburgh's Royal Mile

For as long as Edinburgh has had a visitor industry there have been stories about a secret tunnel running the length of the Old Town, from Edinburgh Castle to the Palace of Holyroodhouse.

Tales were told about Mary Queen of Scots making her way through this passage for covert romantic assignations, and anyone who has been on a ghost tour has probably heard about the soldier sent into the tunnel with a drum, allowing cartographers to map the line of the tunnel by tracking the sound of his drumming from the surface. He was never seen again, but when the nights are still and quiet a ghostly drum can still be heard on the Royal Mile...

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For years, though, no evidence of that tunnel actually existed, and it was dismissed as mere storytelling to thrill visitors.

Until now.

Just before the lockdown came into effect last week, I was one of just a handful of guides from across Edinburgh who were invited to join a 'hard hat' tour led by the archaeology department of Historic Environment Scotland to explore a newly excavated length of tunnel that had been uncovered leading from behind a fireplace in the Victorian-era gatehouse at Edinburgh Castle.

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The fire place had been removed for cleaning as part of the castle's extensive maintenance programme, and a void was uncovered dropping to just below the level of the dry moat that was dug in the eighteenth century, and then runs in a more or less straight line beneath the esplanade in front of the castle, to Castlehill at the top of the Royal Mile.

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The first indications that this tunnel was more than just mythology were discovered in 2011 when new foundations for the seating stands for Edinburgh Military Tattoo were being built into the ground under the esplanade, when a section of rock collapsed exposing a short length of passageway.

Early explorations showed that the tunnel had been badly damaged over the years, but over the last nine years, a team of excavators have been working beneath the feet of the thousands of tourists who visit the castle to clear rock and debris from the passage. ​

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So far the team have excavated approximately 150m of the tunnel, and they are being cautious about how far it may extend to at its fullest.

There's no solid idea of when the tunnel was created, by whom, how far it stretches, or what its purpose was - most likely it was a defensive structure or a military storage area.

Intriguingly, a research team based at the University of Edinburgh have uncovered references to efforts made at the time of the Reformation to provide security for Catholic priests and bishops.

So-called 'priest holes' are a common feature of a lot of historic houses in Britain, providing a hidden space behind wall panels or beneath staircases to shelter religious figures who were vulnerable to persecution. There's a reference in an old record of a similar space, a bunker or "priest closet", developed at the time of the Reformation in Scotland, that may have been accessible from the lower level of St Giles' Cathedral.

The teams are hoping that if that secret space exists beneath the cathedral, it may be part of this network of passageways that could - in theory - have reached all the way along the length of the city, providing safe passage for priests out of Edinburgh. 

Although the team hope to find evidence of the tunnel continuing further along the line of the Royal Mile, for the time being, modern utilities have made it difficult to perform the necessary LIDAR radar surveys necessary to identify if it continues as far as Holyroodhouse.

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Because there is currently only one way into and out of the tunnel there are no plans yet to open the space to the public, but it is hoped that in the future visitors may be able to once again walk in the footsteps (possibly) of Mary Queen of Scots, once more complete excavations have been finished.

Still no sign of that lost drummer, though...

My thanks to Dr Avril Blague and her team from Historic Environment Scotland for inviting me to be a part of this exclusive preview tour.

Explore more of Edinburgh above ground with my private city walking tours!

NOTE: THIS BLOG WAS PUBLISHED ON 1 APRIL 2020.

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