Addressing the Labour Party conference in 1999 Tony Blair said that devolution in Scotland would guarantee the future of the Union. “I tell you,” he said, “that devolution will be, and is, the salvation of the United Kingdom.”

His Scottish colleagues agreed enthusiastically - but their agenda was somewhat different. For them it was the best defence against a resurgent Scottish National Party. Giving the Scots their own parliament would, they believed, spike the Nationalists' guns. One minister, George Robertson, even went so far as to say that devolution would kill independence “stone dead”.

Nearly a decade on, things have not quite worked out that way. Last May, against a background of uninspiring government from a succession of Labour administrations, Alex Salmond's SNP won the election in Scotland, dragging the issue of independence once more into the centre of Scottish politics.

True, his party only managed to gain one more parliamentary seat than Labour and cannot command an overall majority. But by promising a referendum on independence before the end of his first term in office - which means, effectively, in 2010 - Mr Salmond has ensured that it remains a live issue.

Since then, opinion polls have suggested that Scottish voters still remain to be convinced by the creed of independence. Although the figures varied depending on how the question was framed, support tended to hover below the 30 per cent mark, and if the issue of separation from the UK was raised, it was well under 20 per cent. At the same time, support for Mr Salmond and his style of government grew, giving him one of the longest honeymoons in Scottish political history.

Enter Wendy Alexander, a close ally of Gordon Brown, brainy, talented, a “big thinker” on Scotland's economic future. She was elected in August without opposition and presented with the task of rethinking the Labour Party's future - indeed, its entire ideological profile.

On the question of a referendum, she was unequivocal. She and her party were against it. “It is not my politics,” she said — and what is more, she pointed out, the SNP administration was unable to muster enough support for one. In a BBC interview in March she emphasised again that a referendum was not in the interests of Scotland because it would divert attention from the real issues. The party's position was that a legal referendum could only be introduced by the Government at Westminster. Anything else would simply be a form of opinion poll.

In this she was supported by the Scottish Tories, who, as a Unionist party, were against a referendum on principle, and by the Liberal Democrats, who regard devolution as their own creation and remained deeply suspicious of the SNP and its intentions.

Instead, Ms Alexander suggested a commission, supported by the three anti-referendum parties, to examine the future course of a referendum.

Since most polls suggested that a majority of Scots wanted the Parliament to be given greater powers, the commission, headed by Sir Kenneth Calman, a former Chief Medical Officer at the Department of Health, was expected to examine alternatives within the devolution settlement and report back by the end of the year. A referendum was not within the body's remit.

That, until last Sunday, was the settled position of the Labour Party in Scotland and with the Prime Minister grappling with intractable problems of his own, there seemed no prospect of it changing. That day, however, an unsourced story appeared in the Sunday Mail — sister paper of the Labour-supporting Daily Record — suggesting that Ms Alexander and Mr Brown were “considering” support for a referendum.

Interviewed on the BBC Scotland Politics Show, she came out with a comment that took most of her colleagues by surprise and caused consternation at Westminster.

“Of course, there have been tactical discussions on these issues,” she said, adding: “I don't fear the verdict of the Scottish people. Bring it on.” Next day she confirmed that this marked a shift of position, if not a wholesale U-turn, defending her new approach by suggesting that it would dispose of the issue of independence for good. Now, she said, it was the SNP dodging the issue rather than her.

What became clear over the next 24 hours was that very few party members, outside the close circle of Ms Alexander's advisers, had been consulted. Some Westminster MPs said they supported her, but most admitted that her move was a gamble and that the timing of her announcement left a lot to be desired. Some suggested that she had been “bounced” into coming out with her statement. Others said that she, in turn, was attempting to bounce the party's leadership into supporting her new tactic.

Two responses were obviously going to be critical: the first was Mr Salmond's, the second Mr Brown's. The SNP's response came almost immediately: it would stick to the original pledge to hold a referendum some time towards the end of the party's four-year term of office. The Prime Minister's took longer, but when it came, it seemed, on the surface, to cut the ground from beneath Ms Alexander's feet.

Replying to David Cameron at Question Time yesterday, Mr Brown said that Labour's position had not changed. It would await the Calman commission's report and take a view then about devolution. Pressed to respond to Ms Alexander's support for an immediate referendum, Mr Brown replied stolidly: “That is not what she has said.”

The gap between London and Edinburgh has never yawned so wide.

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