Cleave Dyke Defensive System

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Cleave Dyke System

The Cleave dyke system is several Dykes which combine to create a boundary of between 9 and 18 kilometres running north south to the west of Thirsk. To date excavations have found minimal dating evidence, but a pre roman date has been given which means if not built by Venutius the Dyke system was certainly available for use by Venutius. The Dyke itself is in close very close proximity to the hill forts of Boltby and Roulston Scar. Other dykes have been reported to the north and south of this system and it is therefore likely to have been used to define the border and to create a defensive position against possible Roman (or Parisian) attack.

Cleave Dike is the most westerly of a series of cross‐ridge boundary Earthworks that run along the western Scarp of the Hambleton Hills, just to the west of Thirsk in North Yorkshire. Beginning near grid reference SE 501 897, it extends intermittently for some 9 km north–south to SE 519 826, climbing the limestone high ground east of the escarpment and skirting the head of Roulston Scar (heritagegateway.org.uk).

Structure & Form

Where well preserved, Cleave Dike comprises a rubble and earth bank roughly 9–10 ft wide and 4–5 ft high, with a flat-bottomed ditch of about 6 ft width on its east (upslope) side. In places a lower counterscarp bank runs alongside the ditch, completing a defensive profile roughly 15–20 ft across. Variations in width and height along its length suggest that the builders sometimes exploited natural outcrops or re-used earlier features to economize labour (heritagegateway.org.uk).

Geology & Landscape Context

The dyke is set on the Great Scar Limestone of the Carboniferous Askrigg Block, the same bedrock that forms the dramatic escarpments of Sutton Bank and Roulston Scar. Beneath a thin soil mantle, the limestone weathers into angular fragments ideal for constructing stony banks. Above the scarp, the uplands are characterized by dry valleys and Gritstone moors, while below lie the more sheltered pastures of the Vale of Mowbray. Cleave Dike exploits a natural ridge-neck, closing off easy access from the upland plateau into the dale system (historicengland.org.uk).

Date & Archaeology

Though direct excavation has been limited, typological comparison places the dyke in the Later Bronze Age to Early Iron Age (c. 1500–400 BC), a period when many such boundary works were erected across southeast Britain. In the vicinity of SE 5067 8670—where a branch known as Casten Dyke diverges—fieldwalking has recovered Neolithic pottery sherds from pits that pre-date the main bank, hinting at a multi-phased use of the ridge for enclosure and segregation (heritagegateway.org.uk). A small evaluation trench recorded by Spratt (1982) noted charcoal flecks in the ditch fill and occasional worked flints, but no large-scale trenching or geophysical survey has yet been published.

Historical Interpretation

Cleave Dike likely served as a territorial boundary—perhaps between tribal groups such as the Brigantes and neighbouring peoples—controlling movement along the watershed rather than halting livestock outright. Its alignment, parallel to other ridge dykes on the Tabular Hills, suggests a coordinated landscape strategy in the first millennium BC. Later folklore attributed these earthworks to resistance against Roman or “Parisian” incursions, but current consensus sees them as indigenous frontier markers, chosen to reinforce natural divisions and to guard prehistoric Barrow cemeteries on the uplands ( historicengland.org.uk).

Iron Age Borders

Interestingly this defence is some distance from the later Parisi - Brigantes border (other side of York) and may indicate (1) That the Parisii occupied a larger area prior to the Roman conquest, (2) Venutius moved the border to a more defensible position, or (3) the apparent "defending the Barrows" position was deliberate, aimed a providing a defensive wall for the earlier Bronze age barrows. Or a combination of the three.