It's true that hard borders are a modernish (start of c20th) invention, but they're just as often something that labour asks for in order to prevent labour competition. "Taking our jobs" and all that.
They're also products of both the information-state (being able to know who's in the country through identity document systems) and the jet age. Before the steamship the only real border enforcement was on trade at ports.
The British Empire had "freedom of movement" that effectively lasted only as long as people weren't using it in significant numbers. People could move from the colonies to the centre, and indeed after WW2 the government actively solicited Jamaicans to do so (Empire Windrush), but resistance from the public has increased since then.
They're also products of both the information-state (being able to know who's in the country through identity document systems) and the jet age. Before the steamship the only real border enforcement was on trade at ports.
The British Empire had "freedom of movement" that effectively lasted only as long as people weren't using it in significant numbers. People could move from the colonies to the centre, and indeed after WW2 the government actively solicited Jamaicans to do so (Empire Windrush), but resistance from the public has increased since then.