In the end it was Mark Ballard who called it right. “With a couple of weeks to go there’ll be a poll putting Yes in front, then Cameron will come to Scotland and offer more powers” he predicted at the beginning of August. I objected: “there’s no way Cameron could offer more powers without ensuring ‘English votes on English matters’, and there was no way Labour could agree to that”. Surely Labour would have to veto this.

English Vote for English Matters is important for several reasons. Firstly, it seems unjust that Scottish MPs get to vote on matters that don’t directly affect their constituents. As former West Lothian MP, Tam Dalyell put it: “why should I be able to vote on matters that affect people in Blackburn, Lancashire, while I am unable to vote on matters that affect people in Blackburn, West Lothian.” This has had important impacts. The imposition of £3,000 a year fees for students only passed with votes from Scottish Labour MPs. Had it been an England-only vote, fees would have been defeated.

It’s also important because of the way spending is worked out for Scotland. The Barnett formula, which determines how much money the Scottish Government gets in its block grant is worked out on the basis of spending in England. So if Scottish MPs are barred from voting on English matters, they have no say on the funding coming to Scotland. Which would also be unfair. I can’t think of a single bill passed at Westminster since 2010 that wouldn’t have changed the block grant for Scotland.

Since the Conservatives lost more than half their 21 Scottish Westminster seats in 1987, Conservatives have lost any electoral stake in Scotland. They’ve largely given up on winning significant numbers of Westminster seats. This has become even more marked since the 1997 Conservative wipeout. At the 2001, 2005 and 2010 elections Conservatives won a single seat each time. Meanwhile Labour won 41 of Scotland’s 59 constituencies in 2010, taking them close to the Conservative total. This means they can play with a free hand against Scotland. It has lead to a stoking of tensions about senior Labour ministers from Scotland and the vagaries of the Barnett formula.

The stoking of tensions around Scotland’s deal in the Union creates a huge opportunity for the Conservatives: they can portray Labour as the party of Scotland. Because Labour has made such a play of how important it was to ensure that Scotland vote ‘no’ and to do so acting in ‘solidarity’ with anti-Conservative voters in England, this argument has considerable resonance. Labour relies on Scotland not for majorities, but for working majorities. Scotland is vital for a strong Labour government like those lead by Tony Blair.

I was astonished that, when the 51:49 poll came along, Labour were so blinded by the panic over losing Scotland, they didn’t ensure that English votes on English matters was off the table. Ed Miliband joined with David Cameron to make a ‘vow’ to ensure more powers for the Scottish Parliament. It swung the vote back to a ‘no’. But, as we are now discovering, it was a Conservative trap.

And a trap out of which Labour will find it difficult to get. That’s because the Conservatives have no interest in allowing more powers for Scotland: they have no votes to lose. But they can make huge gains in England by attacking Labour’s desire to hold on to the votes of their Scottish MPs on English matters. Door-to-door Labour will be presented across England as a party of Scotland, not one for English people. So Labour will have to sacrifice either the votes of their Scottish MPs or Labour will have to sacrifice their ‘vow’ on more powers for Scotland. That’s why Cameron’s first demand on Friday morning was English votes on English matters.

Either way Labour loses. Reneging on their ‘vow’ will make the seats of their Scottish MPs very difficult to hold. Allowing English votes on English matters will prevent Labour from governing on a whole range of reserved issues, even if they achieve a UK-wide majority. Labour may even have to concede a reduction in the number of Scottish MPs and a ban on Scottish Ministers serving outside departments where the Scottish Parliament has no power. So much for solidarity.

There is no reason whatsoever for Cameron to honour the ‘vow’. By not doing so he makes Labour’s position untenable. Either untenable in England because they are still insisting on more powers for Scotland while Scottish MPs continue to vote on English matters. Or it will be untenable in Scotland because Labour failed to deliver more powers in exchange for Scotland voting ‘No’. He will be entirely unconcerned by SNP or others taking Labour seats in Scotland. And with a stick to beat Labour with on the doorstep in England, Cameron will fancy his chances of winning the 2015 election.