Grimsby Old Blockhouse
Has been described as a Certain Artillery Fort
There are masonry ruins/remnants remains
| Name | Grimsby Old Blockhouse |
| Alternative Names | Tresco Old Blockhouse; Dover Fort |
| Historic Country | Isles of Scilly |
| Modern Authority | Isles of Scilly |
| 1974 Authority | Isles of Scilly |
| Civil Parish | Tresco |
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)
This site is a scheduled monument protected by law
This is a Grade 2 listed building protected by law
Historic England Scheduled Monument Number
Historic England Listed Building number(s)
Images Of England
Historic England (PastScape) Defra or Monument number(s)
County Historic Environment Record
| OS Map Grid Reference | SV897154 |
| Latitude | 49.9585189819336 |
| Longitude | -6.32754993438721 |
| Eastings | 89720 |
| Northings | 15460 |
