41. How high was Hadrian’s Wall?

In the second half of the 16th century, Samson Erdeswick noted a section a quarter of a mile long near Bowness still standing to 16ft (4.8m), whilst Sir Christopher Ridley claimed (somewhat implausibly) it stood to 21ft (‘in sum placis yet vij yardis’). Soon afterwards, Camden recorded a stretch of curtain wall near Carvoran still standing to 15ft (4.5m). The best archaeological clue to the original height of the curtain wall comes from the set of stairs found at Milecastle 48 (Poltross Burn). Although the stairs do not survive to their full original height, a height for the walkway of the milecastle has been calculated at 3.6m (12 Roman feet). Coincidentally, this is the figure Bede gives for the height of the curtain wall. There is, of course, no guarantee that the wall was the same height for its entire length.

If it also had a walkway, it is likely to have been at the same height as that of the milecastle and, if indeed it had walkway, comparison with other contemporary fortified sites suggests it will also have had a parapet of around 1.5m on its northern edge, giving a total height of perhaps 5.1m. However, at Poltross Burn the ground level to the north of the curtain wall is c.1m lower than to the south (a fact now disguised by the railway embankment), so the original height of the north face here, from ground level to the top of the parapet, might have been 6m (20 Roman feet) – coincidentally a common width for the berm. If it did not have a walkway (and thus no need of a parapet), it might still have been the same height, so that it matched the milecastle (which will still have needed a parapet around its wall walk).

Further reading: Breeze and Dobson 2000; Bidwell 2008