In the interest of heightened security, anyone setting foot on the British island will be subject to stiffer security checks.
If you happen to live in Scotland or Wales, you're on the land mass already and you'll not notice any difference.
If you happen to live in Northern Ireland, you'll be treated like any other foreigner. The unionists are outraged. Geography defies them once again.
The fact of the matter is, the six counties in the north are not, in any way, connected to the rest of the United Kingdom. The unity is political, and the planet was not consulted when partition was agreed in 1922.
While Scots and Welsh can move about the U.K. with ease, the poor, beleaguered Northern Irish will be subject to all the same checks and inspections as those arriving from the Republic of Ireland. As much as the unionists would seek to deny it, their little corner of the kingdom is firmly attached to Ireland and no amount of rhetoric can move a large land mass.
Unionists traveling within the U.K., but outside of the island of Ireland, will be asked for identification. A passport will do, but that implies that they're citizens of some other country, and they don't see it that way. The government is planning to accept other documents as well, possibly a national I.D. card, but even that won't go down well with those who love the United Kingdom of England and the little bit of Ireland that used to be important to Westminster but isn't any more because Harland & Wolf stopped making ships.
Geography. Making a mockery of unionism, as if things aren't difficult enough already, what with the Shinners in government and the young people all leaving and the Catholic population climbing. It takes sheer determination to be a unionist these days.