Disgruntled Tories who were flirting with UKIP were warned by David Cameron in the Tory Autumn Conference that in going to bed with Nigel Farage, they risked waking up with Ed Miliband. At the time, that seemed a pretty dreadful prospect – and one which would not easily be usurped in its degree of undesirability.

Since then, the SNP has surged in the polls in the aftermath of the rejection of Scottish independence. The party is predicted to steal as many as 40 seats from Labour in the upcoming election. If such predictions are realised in May, the SNP would be the crucial player in coalition negotiations should neither of the main parties win an outright majority.

Accordingly, a much bleaker reality than bedding down with Nigel Farage and finding yourself next to Ed Miliband the following morning now presents itself. By voting for Miliband, you could wake up sandwiched between both the Labour leader and Alex Salmond.

Miliband is running scared from the West Lothian Question, the issue of Scottish MPs being able to vote on English-only matters, lest he antagonises his future SNP allies, or generally undermines his already much-weakened Labour support base in Scotland. Asked at countless interviews whether he would form a coalition with the SNP, he equivocates. This is a man who is positioning himself to do a deal with the SNP should he fail to gain an outright majority.

Leaving unpleasant metaphors of politicians in the bedroom aside, a Labour-SNP coalition would endanger the already diminished legitimacy of the constitution. SNP involvement in UK-wide government would be anathema to the sixty million or so who do not reside in Scotland. The West Lothian Question would soon become a triviality should Alex Salmond or any other SNP representatives find themselves influencing the formulation of policy at Cabinet level.

Entrusting the reins of UK-wide government to members of a party which continues to support the dissolution of the Union and, moreover, only stands in Scotland, leading to an inevitable bias in its policy, would surely precipitate disquiet amongst the more placid, devolution-deprived English majority in the Union. How can a party which only seeks to stand in one part of the Union, wishing to break away from the other, more populous constituent parts, have any serious credibility in formulating policy which encompasses the whole?

A Labour-SNP coalition is hardly an unduly apocalyptic reading of current polls. Labour, despite losing a predicted 40 seats to the SNP, are likely to remain the largest party in parliament due to the considerable disjunction, favouring Labour interests, between the proportion of votes and the consequent distribution of seats. In this scenario, and with the Lib Dems largely wiped out, the SNP would be Labour’s natural ally in government. Angus Robertson, leader of the SNP in Westminster, is rejoicing at the prospect "of the SNP holding the balance of power in a hung Westminster parliament with a minority Labour government".

Of course, those voting for the SNP would be ecstatic. The surge in support for the party in light of the ‘no’ vote in the autumn referendum attests to the limits of Scottish nationalism. Many who voted no in last year’s referendum, fearful of the consequences of independence and, of course, vindicated by the recent collapse in oil prices which has entirely undermined the ‘Yes’ campaign’s cause, have subsequently turned to the SNP as a means of extracting benefits for Scotland while remaining part of the Union. If you were Scottish, why wouldn’t you? With the SNP forming part of a Cabinet, Trident may be moved to England at great expense, the Barnett formula may be increased, and the West Lothian Question may again be kicked into the long grass – if the SNP finds itself holding the balance of power in May, anti-English/Welsh/Northern Irish policies will be implemented with a breath-taking degree of impudence by Salmond and his beleaguered prop, Miliband.

The Queen allegedly “purred”, according to David Cameron, when hearing the news of the ‘no’ vote last autumn, but perhaps her metamorphosis into a cat was premature. At stake in last year’s referendum was principally the future of Scotland; the rest of the Union would have survived intact if the Scots had voted to leave.

A much greater danger now presents itself at the upcoming general election. The overwhelming majority of the Union may find itself governed by a coalition heavily dependent upon the support of a party which explicitly prioritises Scottish interests above all else, not even bothering to stand outside of the Celtic heartlands. At stake on 7 May 2015 is the integrity of the entire Union.