John McTernan: No Referendum Bill proves our system is working

'I wonder what he meant by that?", was Metternich's famous comment on hearing of the death of Machiavellian French diplomat Talleyrand. Many in Scotland muttered something similar when Alex Salmond confirmed that there would be no Referendum Bill before next May's election. Agenda-setting stroke of genius or historic opportunity missed? Debate raged, but was there a simpler answer?

It seems there was. Government lawyers say it became impossible to draft a Bill that was legally within the powers of the Scottish Parliament. The story goes like this. The primary problem with any referendum passed by the parliament is that the Scotland Act – the legislation framing its powers – states that the constitution is reserved to Westminster.

The initial move to accommodate this was the proposition that any referendum would be "advisory". As a senior Scottish Government official observed to me: "It's not ultra vires to talk about things." And so, a draft Bill was published and a National Conversation launched. But as the Conversation continued a new phrase appeared on ministers' lips, and on press releases, "referendum on independence".

This is where the story gets interesting. Those words were unwise, a senior Whitehall lawyer told me, they go to motive. Scottish Ministers were creating a bank of evidence that could be put to the Judicial Committee of the Privy Council, the ultimate referee on legal disputes between Westminster and Holyrood.

So far it hasn't got there – but Scottish Government lawyers are also concerned about this. Still, they've had a more pressing problem – drafting a Bill that's competent. And this had two major hurdles. First, Elish Angiolini who stayed on as Lord Advocate when the SNP formed their government. She has to give advice to Scottish Ministers about whether a Bill falls within the legislative competence of the Parliament. (Advice which is routinely revealed.)

Now, Ms Angiolini will, and should, have a long and distinguished career after government. But to do so she needs to maintain the respect of her peers in the legal profession. Even were she heavily pressurised politically she couldn't afford to give a "soft" opinion on a Devolution Bill. And the SG couldn't risk publishing a Bill with law officers advice that questioned the Parliament's competence. Deadlock.

The second obstacle was the Presiding Officer of the Scottish parliament, Alex Fergusson. He too has to take a view about whether a Bill is competent. Normally he'd rely on the Scottish Government lawyers – in this case he has been considering external advice.

The Referendum Bill faced an obstacle course that could not be surmounted. Not just the Scotland Act and the JCPC, but internal doubts at professional and Law Officer level, and external constraints too.

This is a much more interesting story than the discussion of whether the First Minister is still a tactical and strategic political genius. What happened was the system working. The checks and balances operating. And all without rumblings, eruptions or rows. How very British, one might say.