Milefortlet 21

Milefortlet 21
Milefortlet 21, with the post-medieval Allonby Saltpans on the seaward side
Location within Cumbria
Type	Milecastle
Coordinates	54°44′48″N 3°27′01″W / 54.746648°N 3.450398°W / 54.746648; -3.450398
County	Cumbria
Country	England
UK-OSNG reference	NY06734004

Milefortlet 21 (Swarthy Hill) was a Milefortlet of the Roman Cumbrian Coast defences. These defences were contemporary with defensive structures on Hadrian's Wall. Its remains exist as reconstructed turf ramparts (to a height of about 1 metre (3.3 ft)) and ditch, reinstated to its original profile (also around 1 metre (3.3 ft)). They are located on a low cliff on the coast, north of the village of Crosscanonby, and just inland from the coastal road. It is the only milefortlet to have been fully excavated and is open to the public.

Milefortlet 21 was a long-axis milefortlet, constructed with 6 metres (20 ft) wide turf ramparts and timber gates. The ramparts were constructed from turf facings revetting a sand core, giving internal dimensions of 14.5 metres (48 ft) by 18 metres (59 ft).

The internal dimensions of the seaward gateway was 3 metres (9.8 ft) square, formed of four posts. Internal to the milefortlet was a road (no evidence of which was found outside the ramparts). To the south-west of the road there were three buildings; all apparently built on sleeper walls and of similar size, but not of the same layout. The seaward two shared a common wall, and the third was free standing. The most seaward contained a hearth, and the central building contained a furnace or oven. To the north-east of the road stood a single building, taking up most of the area, and having dimensions 18 metres (59 ft) by 5 metres (16 ft). The building was apparently divided into four, with the central bays each containing a hearth, and the outer bays each containing an oven.

The milefortlet was surrounded by a ditch on all but the seaward side. The ditch was broken by a causeway at the opposite end.

In 1968 aerial photographs revealed the cropmarks of the milefortlet's ditch. This was 70 yards (64 m) north-east of its predicted site.

In 1990-1991 a full excavation took place. Finds included: black burnished and grey ware (including cooking vessels); Samian ware; part of a bead; a gaming board; a knife; and an unidentified object that was probably an adze. The pottery finds were consistent with a single period of occupation (Hadrianic).