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Old Blockhouse

old blockhouse

The Old Blockhouse on the Isles of Scilly

Perched on a clifftop overlooking the rugged coastline of St Mary’s, Isles of Scilly stands the imposing Old Blockhouse fortress. Dating from the 16th century reign of Queen Elizabeth I, this perfectly preserved slice of history makes for an atmospheric visit.

Whether you’re already exploring Scilly or planning a trip, don’t miss the chance to uncover tales from this historic coastal outpost. Here’s everything you need to visit this impressive island sight.

old blockhouse from above

Getting There

To explore the Old Blockhouse, you’ll first need to make your way out to the beautiful Isles of Scilly!

The quickest way is grabbing a passenger ferry or flight over from mainland Cornwall. Scheduled boats and planes zip over frequently from Penzance from March through October.

The blockhouse sits on the island of Tresco just a 15 minute walk from the capital New Grimsby Town. Head north along the coastal path from Porthcressa Beach located right in the town centre.

Opening Times & Tickets

One of the best things about visiting the blockhouse is that entry is completely free! As an unstaffed ancient monument, you can simply wander around the outside and inside at your own pace daily.

The Old Blockhouse is owned and maintained by English Heritage. Visit them to find out about the benefits of membership.


It’s easily combined with exploring sights around St Mary’s like the Garrison Walls, Daymark sight and Juliet’s Tavern viewpoint which all sit close by.

The Old Blockhouse Story

The Old Blockhouse, also known as the Dover Fort, was constructed between 1548 and 1551 by the government of Edward VI to safeguard the islands against potential French invasions. The blockhouse, built of granite, was designed to accommodate a battery of two or three artillery pieces on a square gun platform situated on a rocky outcrop, overlooking Old Grimsby harbor and the anchorage of St Helen’s Pool.

An earthwork bank and a stone wall were erected to protect it from attacks from the beach and the landward sides. A small room was later added to provide living quarters for the garrison. The construction of the Old Blockhouse was part of a broader effort to fortify the Isles of Scilly during the reigns of Edward VI and Mary I, which included the attempted construction of a large artillery fort known as Harry’s Walls on St Mary’s.

old blockhouse from above

The Old Blockhouse did not see action until the 17th century, during the English Civil War. In 1651, a Royalist garrison defended the islands against an attack by a Parliamentarian fleet commanded by Admiral Blake. The blockhouse, however, proved of little value against the longer-range guns of Blake’s ships. It was subsequently replaced by a much stronger gun fort.

The Old Blockhouse is currently in a ruined condition and is owned by English Heritage. The site is defended by a U-shaped rampart, with two lower ramparts surviving lower down, covered in blown sand.

The approach to the blockhouse is visible as a turf-covered bank up to 33 feet wide and 6 feet high around the crown of the hill.The construction of the Old Blockhouse and its role in defending the Isles of Scilly provide valuable insights into the military history and coastal defense strategies of the 16th and 17th centuries.

Plenty of information signs now tell the tales of its history to visitors. Marvel at how this small fort could accommodate a garrison of 12 soldiers up until the early 1800s!

old blockhouse isles of scilly

What to See & Do

At this free-to-access historic site, visitors can walk around inside the tower and soak up information on displays. Admire the formidable sea views that surround the building too for some epic photos.

Top highlights include:

  • Reading about the various rooms & life here
  • Checking out the restored cannons nearby
  • Climbing up onto the stunning roof platform
  • Imagining firing at enemy ships of old!
  • Admiring the uninterrupted sea views

While access is available year-round, visiting in dry weather allows properly exploring all levels. Be careful touring the exposed roof in particular during very windy or rainy spells!


Frequently Asked Questions

Are dogs allowed at the Old Blockhouse? -Dogs on leads are welcome

Is it wheelchair accessible? – There are steep and uneven steps up to the Blockhouse entrance, with sheer drops from inside the ruins.

Is there a gift shop or cafe? – No, there are no facilities at the Old Blockhouse. Plan accordingly!

How long does it take to visit the Old Blockhouse? – You may want to sepnd longer enjoying the views, but allow an hour for your visit.

blockhouse from beach scilly

Other nearby locations to visit

  • Tresco Abbey Gardens – Catch a short boat trip to stunning car-free Tresco to explore the breathtaking subtropical Abbey Gardens, which contain exotic plants from 80 countries that rarely flower in the UK.
  • Cromwell’s Castle – This ruined 17th century artillery fortress offers striking views over Scilly’s islands from the circular gun platforms leftover from the Civil War era.
  • King Charles’ Castle – Also close by sits this picturesque ancient ruined coastal fort, accessible from the northern tip of Tresco at low tide and providing panoramic scenery.
  • Porthcressa Beach – One of the most stunning white sand beaches in Scilly conveniently located in St Mary’s near Hugh Town, with gorgeous turquoise waters perfect for swimming or watersports.
  • St Mary’s Boatmen Trips – Take relaxing wildlife spotting or inter-island hopping boat trips with qualified local experts to see puffins and seals among Scilly’s uninhabited islands and secluded coves.
  • Isles of Scilly Wildlife Trust – Join a Wildlife Trust guided walk or boat trip to explore the diverse birdlife, marine mammals and flora found among Scilly’s many uninhabited tiny islands like Annet or the Eastern Isles.
  • St Martin’s Vineyard – Catch a boat to the northernmost inhabited island St Martin’s, the only island vineyard in Scilly growing grapes well-suited for winemaking in the unique terroir.

Whether you’re already exploring magical Scilly or planning a trip, don’t pass up visiting the impressive historic blockhouse fortress. Kids will revel in this secret hideaway imagining the soldier’s lives here centuries ago! And parents can admire the old-world charm, unique history and dramatic views too.

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