The historian Iain McLean once memorably referred to the West Lothian Question and Barnett Formula as like "two mad men in the attic".

 

Everyone, ran the simile, knew they were there because they could hear them moving around, but at the same time no one was prepared to do anything about them.

That was true for a long time, although of late there's been something a response. The Barnett Formula, once spoken of by Scottish Tory leader Ruth Davidson as being in its death throes, has been filed under "too hot to handle" by the Unionist parties and ring-fenced by 'the Vow'.

But the other mad man, the West Lothian Question, has become a whole lot noisier. Last week the Leader of the House, William Hague, set out options for answering it, all of which involved some sort of "decisive say" for English MPs on England-only legislation.

As I've argued before, this is an odd strategy for a supposedly Unionist Government to pursue, for the equality of MPs, no matter which part of the Union they hail from, is an obvious piece of procedural and parliamentary glue. Dissolve that and the UK becomes weaker rather than stronger.

Interviewed on Radio 4 recently, Mr Hague's confusion was obvious. "We have to decentralise power within the United Kingdom,' he told the historian Peter Hennessy, "but in a way that makes people happier that they are part of the United Kingdom".

To an extent, so-called English Votes for English Laws (Evel) addresses a problem that doesn't really exist; that is, England-only legislation being passed on the basis of support from Scottish MPs. As recent analysis has shown, only in a handful of cases has this happened in the past few decades.

Conservative MPs, however, argue that some of those cases were significant, for example top-up fees and foundation hospitals, while the perceived unfairness of the West Lothian Question is certainly felt south of the Border, where polls show Evel to be both popular and salient. Therefore the issue, as Mr Hague has observed, needs to be faced.

But it will only happen if the Conservatives win a majority at next May's General Election and that isn't a done deal. As one senior Tory source told me, every scenario is conceivable five months out from polling day. The Liberal Democrats, with a disproportionate number of Scottish MPs, are against, as is Labour for similar reasons.

Alex Salmond, giving interviews to London-based newspapers as if he were already an MP, recently clarified his thinking on Evel, arguing that SNP MPs may set aside their present informal abstention in order to support a Labour administration come May. As on so many other issues, the Nationalists face in two directions at once.

Thus the SNP's approach to Evel is driven by pure opportunism, allowing its MPs to vote on some England-only issues (including top-up fees a few years ago) while abstaining on others, usually because they're a bit tricky, the best example of which was the English gay marriage legislation. Pete Wishart, SNP MP for Perth and North Perthshire, maintained it didn't relate to Scotland when in fact several clauses were directly applicable north of the Border.

Mr Salmond's comments on Evel, however, have (as one Labour MP put it) "more to do with campaigning than governing". Abstaining from England-only votes would, of course, make an enlarged block of SNP MPs pretty useless in a hung Parliament but, more to the point, the former First Minister has (since September 19) gone out of his way to avoid his party being squeezed, as usual, in a Westminster election.

Depicting the SNP as the power broker in a "balanced" parliament has, to varying degrees, been its pitch at every election since 1983, only this time it appears much more likely. Labour is conscious its usual doorstep argument of "vote Labour to get rid of the Tories" is much less salient given the obvious retort "well, we tried that last time". Nevertheless it remains true: the fewer Labour MPs in Scotland there are then the more likely it is David Cameron remains in Downing Street.

Which is, of course, the SNP's preferred scenario. For all its talk of supporting a Labour government, Nationalists realise that another Conservative government, preferably with a majority, enhances the possibilities of another independence referendum. Mr Salmond has already spoken of an in/out European referendum in 2017 as the tipping point that could bring about another poll but that, of course, is predicated (like Evel) on the Tories winning a majority.

It's striking that an ex-SNP leader is making the weather when it comes to the party's election strategy, although the new First Minister has made it crystal clear her MPs wouldn't support a minority Conservative government under any circumstances. Her conditions, meanwhile, for supporting Labour are quixotic: only if Ed Miliband (whom Mr Salmond regards with contempt) agrees to scrap Trident and "end austerity'" will they countenance a parliamentary pact.

That, like the Scottish Government approach to the Smith Commission, basically sets up any Labour/SNP partnership to fail but then, as I've written, with the SNP's unstated but preferred scenario of a Tory government, all this becomes academic. A Labour majority, meanwhile, isn't to be dismissed. As an opinion poll showed yesterday, Mr Miliband's party now has a seven-point lead over the Conservatives.

That would represents the worst outcome for the SNP. With a Labour majority at Westminster, both Evel and an in/out EU referendum become much less likely (though not impossible). As one senior Labour source put it to me, "we're going for a majority", while another made the point that, with the Conservatives intent on a "divide and conquer" constitutional strategy having embraced Evel and greater fiscal autonomy, "only Labour is now advocating continuing economic and social partnership".

The prospects of a long-overdue (and more holistic) approach to the UK constitution have also receded as a result of this post-referendum dynamic. Although Mr Hague has made reasonably positive noises about a constitutional convention (something also supported by Labour and the LibDems) he's said such a process couldn't include Evel, the Smith Commission, events in Northern Ireland or the Silk process in Wales.

As one minister (who has long supported a more "coherent" approach) told me: "It's become about managing events in each part of the UK, so the opportunity to take a step back isn't necessarily there." This is concerning, for the constitutional terrain is becoming ever more cluttered. In Greater Manchester, for example, Westminster is pushing ahead with more devolution, also desired by the core cities group of the UK's largest local authorities (which includes Glasgow).

Mr Hague said last week that we shouldn't worry about "creative thinking" when it comes to constitutional reform. He is surely correct, but without a less ad hoc and reactionary approach, the noise from the mad men in the attic will only grow louder.