Multiplication

This is becoming silly. The Scotsman makes up new constitutional rules:

HOW many referendums might it take for the SNP to secure an independent Scotland? One in Scotland might seem the obvious answer. But a change in the British constitution would require a UK-wide referendum, too. A third may be required to ratify the negotiated settlement, which could turn out to be significantly different from popular preconception. Assuming the answer to all of these is "Yes", a further referendum may then be required on whether an independent Scotland should apply for membership of the EU, from which most legislation now emanates anyway, taking the final tally to four.

Since when did constitutional change 'require' a referendum? It may be politically convenient to have one on certain types of changes, but in no sense is it 'required'.