22. Was Hadrian’s Wall the first frontier in Britain?

Various lines have been claimed as early ‘frontiers’ for Roman Britain, starting with the Severn–Trent (or Fosse Way) line, the Gask Ridge in Scotland, and the Stanegate in Northumberland and Cumbria, but Hadrian’s Wall is undoubtedly the first mural barrier and, as such, an indisputable frontier. Most of the other claimants can be dismissed as fortified roads by the sceptical.

Further reading: Breeze and Dobson 2000