@McTag,
What does it mean Mac--Scotland secedes?
Might it mean that all the Scots living in England will have to choose citizenship and the ones who stay Scottish will be aliens with the same status as other aliens.
What do you think Northern Ireland would do in that event?
Or that a Scottish government could sign a defence pact with, say, Russia? It could hardly defend itself.
It's influence on our Security Council seat at the UN would vanish.