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Harry’s Walls – An Unfinished Tudor Artillery Fortification

On the hill known as Mount Flagon, overlooking the harbour in St Mary’s sits Harry’s Walls.

A mid sixteenth century artillery fort that was never finished, Harry’s Walls is wrongly attributed to King Henry VIII. It was actually started in 1551 during the reign of Edward VI.

The Placement of Harry’s Walls

Throughout the medieval period the main settlement on St Mary’s was Porthennor, now known as Old Town. There was a small castle on the hillside overlooking the sheltered bay. There was also a stone quay extending into the water for larger vessels to moor and offload cargo.

During the late medieval period, and the early Tudor years Naval ships grew in size. This along with the growing unrest between England and the Catholic countries of France and Spain meant that the harbourage at Porthennor became less and less viable. The settlement moved across to Hughtown, and defensive work began to protect the waters of St Mary’s Pool.

Much of the stone from the old castle was robbed out to help build the new quay, and construction was started on an extremely modern design of artillery fort. Harry’s Walls.

The Structure of Harry’s Walls

harry's walls plans

Plans were drawn up for the new fortification by John Killigrew, Captain of Pendennis castle in Falmouth. His instructions stated that it should be built on “the little hill betwixt the freshe water and St Marie Roode”

The plans show a square construction with triangular bastions on each corner allowing artillery to both protect the structure itself from attack, but also to have a passable view of the new harbour. This was the first of its type in the UK, and followed a design that had recently been introduced in Italy. However it was never finished.

The Failure of Harry’s Walls

The commonly accepted reasoning for the fortifications to not have been completed was that the location was not viable.

The C18th Antiquarian William Borlase was heavily critical of the location calling it injudicious and poorly chosen. A history of the islands published in 1796 by John Troutbeck says “If this fortification had been finished it would have been little use, being placed too fsar within the head-lands, and commanding none of the sounds to any effect.”

A more modern analysis suggests that there was no one single place that would have been adequate, and that Harry’s Walls would likely be one of at least a pair of artillery stations working together. Which of course begs the question, why were they never finished?

The simple answer is money. Harry’s Walls was one of many fortifications started during that period, and the young King Edward VI only reigned for five years. On his death England became Catholic once more and the threat of invasion from France and Spain passed. There was little point in spending the large amount needed to complete the site.

Alternative sites

An Alternative to Harry's Walls

Rather than spend the money necessary to defend the anchorage of St Mary’s Pool when the threat of war had receded there was a simpler option. The main harbour was moved to the channel between Tresco and Bryher and the blockhouse on the summit, which was already complete offered all the protection needed.
When Elizabeth took the throne, and the threat of war became real once more, an alternative site was constructed on the Garrison. Star Castle.
A lot of the stone for the new castle was robbed out from Harry’s Walls, leaving it looking much as it does today.

The Standing Stone

Standing Stone by Harry's Walls

On the headland, standing next to the navigation mark is a large standing stone. It is known as the Mount Flagon Menhir. Troutbeck describes it in situ and says that it was supposedly set up as an object of “druidic superstition”. The stone is indeed prehistoric in origin. It has however been supported by the addition of a foundation in more modern times. Presumably because of its use as a navigation aid. It has of course been superceded by the modern navigation mark there today.


Whatever your feelings about Harry’s Walls. Perhaps you believe it was ultimately a folly built in a poor location. Perhaps you believe it was simply rended unviable by the changing political climate. Either way it is well worth a visit.

Harry’s Walls is accessible from the footpath that runs around the back of Porthmellon beach. It is a short walk and it’s worth taking a picnic and spending a moment or two enjoying a very impressive view.



Martin is the creator of About Scilly. He visited the islands for the first time 15 years ago and fell in love. He's been back every year since and would dearly love to live there.

2 thoughts on “Harry’s Walls – An Unfinished Tudor Artillery Fortification

  • August 25, 2018 at 10:08 am

    Suggest you correct the Americanised spelling ( harbour? )

    • Martin
      August 25, 2018 at 11:15 am

      Thanks for the heads up, editing one’s own writing is always a bit of a problem. I tend to see what I think I wrote, not what I actually wrote!


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