Grimsby Old Blockhouse (The Gatehouse Record)

Also known as, or recorded in historical documents as;
Tresco Old Blockhouse; Dover Fort

In the civil parish of Tresco.
In the historic county of Isles of Scilly.
Modern Authority of Isles of Scilly.
1974 county of Isles of Scilly.
Medieval County of Isles of Scilly.

OS Map Grid Reference: SV89721546
Latitude 49.95852° Longitude -6.32755°

Grimsby Old Blockhouse has been described as a certain Artillery Fort.

There are masonry ruins/remnants remains.

This site is a scheduled monument protected by law.
This is a Grade 2 listed building protected by law*.

Description

Old Blockhouse, as it is known, was built between 1548 and 1552 as a raised gun platform with adjoining living quarters. In 1652, it was referred to as 'Dover Fort' in a Parliamentary Survey of Scilly. The blockhouse is situated on a low headland at the south east edge of Old Grimsby Harbour, on the east coast of Tresco. It commands a field of fire to the north west, across the harbour and to the north east between Tresco and Tean. The blockhouse forms part of a series of fortifications built on Scilly between 1548 and 1554 in response to threats from the French. A second blockhouse, now known as Cromwell's Castle, was built on the other side of the island. In 1651, during the Civil War, the blockhouse was used by Royalists to mount heavy gunfire on Parliamentary forces attacking the adjacent stretch of Tresco's north eastern coastline. It is recorded as still in use in 1750. The blockhouse consists of a gun platform of four unequal sides, which is paved with hard standing on the north west and north east sides for artillery. The platform is defined by a parapet, one metre thick, with splayed openings for guns known as embrasures. The blockhouse was built of randomly coursed granite walling with more regular quoins. A storage chamber, probably for ammunition or gun powder, is built against the south east wall. The blockhouse was defended from landward attack by a single semi-circular rampart around the western and southern crest of the headland's summit. It is visible as an earthen bank up to 10 metres wide and 2 metres high externally. Coastal erosion along the headland east of the blockhouse has revealed mortared walling within deep deposits of blown sand. These are thought to represent lines of seaward defence for the blockhouse. (PastScape)

Sources of information, references and further reading

National Heritage List for England Scheduled Monument Number 1013662, Legacy Scheduled Monument Number 15406
National Heritage List for England Listed Building number(s) 1219196
Historic England (PastScape) Defra or Monument number(s) 303400.
County Historic Environment Record (or Sites and Monuments Record) number(s) 7365.

Websites (Gatehouse is not responsible for the content of external websites.)
- English Heritage
  Historic Cornwall
Books
- Bowden, Mark and Brodie, Allan, 2011, Defending Scilly (London: English Heritage)
  Campbell, Adele (ed), 2004, Heritage Unlocked; Guide to free sites in Cornwall and the Isles of Scilly (London: English Heritage) p. 82-3
  Salter, Mike, 1999, The Castles of Devon and Cornwall (Malvern: Folly Publications) p. 16
  Pettifer, A., 1995, English Castles, A guide by counties (Woodbridge: Boydell Press) p. 208 (slight)
  Laws, P., 1980, The Buildings of Scilly (Redruth)
  Troutbeck, J.A., 1796, A survey of the ancient and present state of the Isles of Scilly p. 133
Periodical Articles
- Bowden, Mark and Brodie, Allan, 2011, 'Defending Scilly' Research News No. 16 p. 8-11 online copy
  Brodie, A., 2010, 'The Tudor Defences of Scilly' English Heritage Historical Review Vol. 5 p. 24-43
Guidebooks
- O'Neil, B.H.St.J., 1950, Ancient Monuments of the Isles of Scilly (HMSO) p. 20
Primary (Medieval documents or transcriptions of such documents - This section is far from complete and the secondary sources should be consulted for full references.)
- SP16/368, No. 110 (Survey of 1637) The National Archives reference
Other sources: Theses; 'grey' literature; in-house reports; unpublished works; etc.
- Bowden, Mark, 2011, Isles of Scilly: Military Defences, 1540-1951: Earthworks and Minor Sites (English Heritage Research Department Report series 56-2011) online copy

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The bibliography owes much to various bibliographies produced by John Kenyon for the Council for British Archaeology, the Castle Studies Group and others.

Suggestions for finding online and/or hard copies of bibliographical sources can be seen at this link.
Minor archaeological investigations, such as watching brief reports, and some other 'grey' literature is most likely to be held by H.E.R.s but is often poorly referenced and is unlikely to be recorded here, or elsewhere, but some suggestions can be found here.

The possible site or monument is represented on maps as a point location. This is a guide only. It should be noted that OS grid references defines an area, not a point location. In practice this means the actual center of the site or monument may often, but not always, be to the North East of the point shown. Locations derived from OS grid references and from latitude longitiude may differ by a small distance.
Further information on mapping and location can be seen at this link.

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*The listed building may not be the actual medieval building, but a building on the site of, or incorporating fragments of, the described site.

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