How long was Hadrian's Wall?

"Cruel barbarian invasions", sort of like the Romans, who built the wall, did in invading in the first place and committing various atrocities (such as those which led to Boudica's revolt)?

Dave Wheeldon I I, It's called broadening your knowledge

It does not matter which measurements are used, but don't mix them. That is confusing.

Okay everyone complaining about America-centric questions...