Wendy Alexander has been clear and consistent in her support for a constitutional referendum, one of her allies insists. This was not a U-turn. No, it was just that she hadn't previously spoken publicly about it.

Perhaps the Scottish Labour leader shared her views with her toddler twins, reading the bedtime tale about shooting Alex the Wily Nationalist Fox.

But when she appeared to stumble into the biggest constitutional gamble in recent history, during a BBC interview on Sunday, it came as a surprise to others.

Even she seemed to take herself aback. At first there had been "tactical discussions". Then she was wasn't ruling out support for a ballot. And then she was nonchalantly taunting "bring it on" - why was Alex Salmond scared of the verdict of the Scottish people?

It was later claimed the issue had been forced by a Sunday newspaper article, saying Labour was poised to call Salmond's bluff.

But this was unsourced and there was no need for Wendy Alexander to change recent opposition to a referendum: "Because I don't believe in independence, it's as simple as that It's not my politics Those who want it should argue for it".

This newshound sought more. Was this cleared with cabinet colleagues? Er, not as such, was the reply How about the Labour MSP group? Soundings were taken last September, and, "broadly speaking, there is a majority who support a referendum". Will Labour now push for a third referendum question, asking if people want enhanced powers for Holyrood within the UK? "You're getting ahead of yourself on that."

I offered a clue: they would be mad not to, as that option depresses independence support. "Oh, yes - well, probably."

But yesterday, the leader preferred a straightforward: "independence: yes or no".

One MSP said this is not so much party policy as "open for discussion". No kidding.

How about the Westminster leadership: is Gordon Brown up for this, or has his dithering on SNP strategy led to him being effectively bounced?

"You'd have to ask Downing Street." So I did, and was told the Prime Minister is unpersuaded.

Another Whitehall source responded: "We're leaving Wendy to do the talking on this."

Now, there is nothing wrong with surprises. The grim, grinding predictability of Gordon Brown is a voter turn-off.

They like politicians who tend to go off-message, mis-speak and take occasional risks; Boris Johnson, it seems, or Tony Blair on Clause Four.

But the Wendy U-turn was a new kind of risk, not so much leading from the front as from behind the sofa after a poll drubbing.

Her LibDem allies in the constitutional commission condemned it as panic, putting tactics before principle.

Indeed, if Nicol Stephen were that flexible on a referendum, he could have been in government over the past year.

And what is the SNP to make of it all?

If it tables referendum plans, Wendy will vote for them, but will her MSPs? And is there now a Holyrood majority for a referendum, or not?

One of the more thoughtful Labour musings on its referendum dilemma reckons the SNP wins either way. This is based on the assumption - liable, no doubt, to furious denial - that the Nationalist leadership would privately like to tone down its commitment to blatant Braveheart-style frrreeeedom.

Party woad-wearers won't let them, but some admit it holds them back electorally.

So either an independence referendum says "yes", which is fine by the SNP, starting negotiations on splitting the British family silver, or after a "no" Alex Salmond accepts the Scottish people have spoken and a referendum is a once-in-a-generation opportunity (a period he recently defined as 18 years).

He then tells his party they should rethink independence.

Yes, Scotland should have more autonomy, control over oil, tax and so on, but it could be within a much looser federation of united kingdoms (his preferred monarchist construction nowadays, no doubt to avoid scaring the Household Cavalry).

There is an opportunity for Scotland to create a new type of nationhood, somewhere between the current UK relationship and that which exists between European Union members.

For the SNP, it could have a similar effect to the decision, 20 years ago, to back independence in Europe, instantly blunting the charge that Scotland would be isolated behind border guards, with no trading partners.

Celebrating a year in power, their opponents in disarray, Nationalists may wonder why they should give up dreaming of the trappings of nationhood so readily.

But in reality this scenario frightens Labour more than them, because this shift - similar to those by independence movements in Quebec and Catalonia - could put Nationalists in the Scottish driving seat for decades.

Has Wendy Alexander thought this through?

Perhaps she has; clearly, consistently, but privately.