Once upon a time referendums were seen as ‘unBritish’, as the sort of thing that continental Europe and dictatorships did.

Now we seem to talk of little else. Trust in politicians has declined and a rise in the use of referendums (two UK-wide polls, three Welsh, two Scots and two Northern Irish votes since the 1970s, along with a host of local votes) and combined and reinforced each other.

Politicians interest in direct democracy is driven by what they think the results will be. Tory interest in locally elected police commissioners is influenced by their belief that voters support hard-line law and order policies. The same is true of the Westminster coalition’s ‘referendum lock’ on any new transfer of powers to Europe, shaped by faith in a Eurosceptic public saying ‘no more’.

A Scottish independence referendum is now inevitable. It is agreed by all sides as the best way to decide the issue. Therein agreement ends.

The Scottish Government is committed to holding a vote, possibly with two choices, ’devolution max’ (for full fiscal independence only) and complete political independence. The UK Government is growing increasingly tired of what it sees as the Scottish Government’s politicking and has indicated if a vote is not held soon, it may initiate its own ballot.

Leaving aside legal niceties about ‘the constitution’ from academics such as Adam Tomkins of Glasgow University and Robert Hazell of UCL and the fact that all referendums in any part of the UK are ‘advisory’, this is about political calculations. Until May 2011 the SNP never thought they would be able to get a majority in the Scottish Parliament for a referendum.

The three anti-independence parties, Labour, Lib Dem and Tories, were against an independence poll until May this year. Then the moment the SNP won an outright majority in the the Scottish Parliament - and with it the unilateral power to call a referendum -  they suddenly became convinced of the need for an immediate poll and have shown impatience with the thought of any delay.

The UK Government has indicated that it is considering a poll on independence. The decision will depend on what the Scottish Labour Party thinks after its leadership contest on December 17. Whitehall sources have indicated that there is "no secret plan" at the moment, but that if Labour comes out in favour, this would be "a totally different kettle of fish".

A Westminster initiated poll would be a dramatic intervention and would be seen by many as a violation of the Scottish political environment and end of the UK Government’s ‘respect’ agenda.

Such a vote would in its current context be a pre-emptive vote aimed at closing off political discussion and change. Even if the question were seen as neutral and drawn up by the Electoral Commission with no talk of ‘a separate Scotland’ it would still carry with it the prospect of being seen by many as illegitimate or partisan politicking.

An important precedent is the 1973 Northern Irish referendum, known as ‘the border poll’ on whether the province should remain part of the UK or join the Republic of Ireland. The poll was boycotted by the nationalist community and resulted in a 98.9% pro-UK vote, producing a meaningless result.

A less dramatic, but equally important precedent would be the 1979 Scottish devolution referendum with its arbitrary threshold that any 'Yes' vote would have to be more than 40% of the electorate, widely seen at the time as gerrymandering of the worst kind.

The lessons of 1979 offer another lesson. The forces against independence would in any future vote range across the political spectrum. Many of the more thoughtful voices would argue that a ‘No’ vote did not preclude further significant constitutional change.

In 1979 Alex Douglas Home and prominent anti-devolution campaigners promised that a ‘No’ vote was not the end of devolution and that a better scheme would be brought forward, a ‘Plan B’. It did not exist and ‘No’ meant ‘No’, and we had to wait a further twenty years for change.

A ‘Yes’/’No’ independence vote has the advantages of clarity, but it needs to have legitimacy, be seen in context, and not viewed as closing off the possibilities of other constitutional change.

The politics of this are hugely important. If a Westminster initiated vote is called in Scotland, it be because the Tory-Lib Dem governing Coalition persuades Labour to agree. 

This would be a crossing of the rubicon moment for Labour. If it endorses such a proceedure it will in all probability become tainted by the association with the Tories, and be seen as part of a pan-unionist front.

This matters on two levels. Labour supporters have long claimed that it is not a ‘unionist party’, but one of a wider than nationalist social democracy. Thus any such support for a Westminstercentric referendum could shift the perception of Labour from being seen, as it was in the 1980s and 1990s, as an anti-Tory party to being viewed primarily as an anti-Scottish Nationalist party.

One of the underlying influences of Scottish politics is the continued toxicity of the Scottish Tories and lack of legitimacy of any Tory-led UK Government in Scotland where the Tories attract miniscule levels of support. A Labour move to support a 'Tory' referendum would leave the party forever vulnerable to attack from the SNP, and leave the latter uncontested with the mantle of Scotland’s anti-Tory Party.

There is panic, opportunism and a loss of patience in the UK Government’s consideration of an immediate referendum. You can feel it in Chancellor Osborn's sudden complaint today that the 'threat' of independence is harming inward invetsment in Scotland. This is part of a wider context of a crisis of unionism, itself part of a longer-term decline of Westminster's standing across the whole of the UK including England.

The mainstream British political parties and their Scottish colleagues need to articulate a new vision of Britain, which tells a positive tale of the benefits and gains of the UK for all its citizens.

This version of Britain would have to be far removed from Gordon Brown and David Cameron’s nebulous concepts of ‘Britishness’ or its traditional symbols of empire, imperial delusion and ‘punching above our weight’ across the world. Instead, they would need to pose the UK as a civic and social union, a partnership of equals based on respect, evolving from an old-fashioned marriage into a modern, open arrangement, a co-habitation of nations.

A Westminster initiated referendum in Scotland would not aid such a positive case for the union, rather it would reinforce its association with negativity and fear. This would further diminish the levels of trust Scottish voters feel towards the British state. In such a situation, the pro-union forces may win the immediate battle, but they would lose the wider fight for a democratic Britain.