Last week, Labour signed up to the version of English Votes for English Laws proposed by the McKay Commission – or seemed to.  “We should look at Sir William’s approach of an English (or an English and Welsh) committee stage because it is right that English MPs have a key role in considering such legislation,” Hilary Benn and Sadiq Khan wrote [my italics].

“The political balance on this committee would need to reflect English (or English and Welsh) MPs as a whole and ensure all English regions were represented. Done in the right way, this would be a sensible reform which would strengthen England’s voice without ending up creating two classes of MP,” they added. [My italics again.]

David Laws has called separately for any such committee to be “put together on the basis of proportional representation”.  The Education Minister was presumably fingered for the task to emphasise that this is the position of the Liberal Democrats as a whole, since he is seen as one of the closest of his party’s MPs to the Conservatives.

In principle, the Scottish Nationalists, Plaid Cymru and the Northern Ireland parties should allow England’s business to mind itself.  But it will scarcely be surprising if they query what that is – and question how differences can be established between what is English Parliamentary business and what is the United Kingdom’s.  The non-English parties are bound to treat EVEL as a piece on their chessboard.

I set out the positions of these parties to make the point that the Commons vote on EVEL that is being trailed this morning is not a shoo-in for the proposal.  William Hague will apparently present four options to the Commons.  First, what I call “Soft EVEL” – that’s to say, the McKay proposal, whereby an English Committee stage on designated bills is followed by a vote of all MPs at later stages.

Second, there is “Hard EVEL”, in which only English MPs vote not only at committee but at those later stages.  Third, there is a proposal to give English a veto over certain legislation.  And fourth, there is the Liberal Democrat plan.  This is a reminder that there is no Government position as whole.  Tory MPs want a vote on the proposals early in the New Year.

It may be that there is sufficient voter pressure on Liberal Democrat MPs in England to ensure that some form of EVEL passes the Commons.  However, I doubt it: the other parties will not want to give the Conservatives what would be a much bigger say in English legislation – a consequence of EVEL under any manifestation.

As it is, Labour and the Liberal Democrats are set to quibble over the composition of any English Grand Committee – Labour over a lack of regional balance (as they see it), the Liberal Democrats over the lack of proportional representation.  If EVEL does not triumph, expect Tory backbenchers to dig their heels in over more powers for Scotland.

There is plenty for them to be uneasy about.  David Cameron’s quid pro quo for the EVEL proposals is that 16 year olds will vote in Scotland’s elections in 2016 – a concession to the SNP.  True, they participated in the independence referendum.  But this new decision has knock-ons for the rest of the UK.  If 16 year olds can vote in Scottish Parliamentary elections, why not in English local ones?

ConservativeHome hopes that the Commons will vote for the harder form of EVEL.  But the combination of a blue legislature for England and a red UK-wide executive wouldn’t be sustainable for very long.  It would be a stepping stone towards a federal solution for the UK – the solution outlined in the ConservativeHome Manifesto.

This would in turn raise the future of the Lords.  Any reform of the two houses could render a written constitution unavoidable, since their functions would require clarification.  The Conservatives are proposing changes to the ECHR which could lead to Britain leaving it altogether.  David Cameron has pledged a referendum on our EU membership as a condition of returning to Downing Street.

In the meantime, all the main parties are agreed on more local devolution in England.  George Osborne and Greg Clark’s announcement of a city mayor for Greater Manchester is the shape of things to come.  With so many constitutional pieces awry on the reform table, only a constitutional convention – with added direct democracy – can provide the legitimacy to put them in order.