The Scottish National Party has shredded the infinitely complacent declarations of September 19, 2014

Now the question falls to that institution. The Scottish National Party has made a mockery of all assumptions. It has shredded the infinitely complacent declarations of September 19, 2014. The Scottish voters who heard they were best beloved partners in a Union of equals, with full rights in all its works, have gone about their democratic business. What say the Commons now?

In the only part of the General Election it could contest, the SNP has won almost all that could be won. That tells us where we are. First, says history, the old Liberals ceased to be a force in Scotland; then Tories became an endangered species. Now a question hangs over the very survival of Labour in places it claimed as its own. The SNP will return 56 MPs to Westminster. Westminster and all it represents must decide how to respond to that.

We know one thing already: much of what was said by parties of the Union last autumn was expedient, dishonest, and contemptuous. The instant the referendum result was known, paper hearts were plucked from sleeves. By the morning after, David Cameron was standing in Downing Street declaring that "English votes for English laws" was the truly important issue. Ed Miliband and Nick Clegg were not far behind in assuming that nothing more needed to be said about the Scottish nuisance. This was stupid.

It involved, in fact, a special kind of stupidity from men who had shown us their bleeding hearts while stopping up their ears to what had gone on in the referendum campaign. You could describe the phenomenon in 100 ways, but one way would be this: we will have our self-determination, said 44.7% of referendum voters to those parties of Union, because we will no longer have you. It was a clear enough message. And those parties didn't bother to listen.

They thought their problem had been fixed. They thought those Yes voters would calm down, "move on", reconcile themselves to defeat, lapse into amnesia, and soon enough drift back into old political habits. Labour even invited the alienated to "come home". It was like being told to give thanks for inheriting a haunted house. The 44.7% vote was about many things, but it was above all an unambiguous act of rejection. In the weeks after the referendum, that truth was ignored.

When the truth began to sink in, things became blackly comical. Annoyance became petulance. As the SNP surge took on the looks of a tidal wave, petulance became a thrashing fury. Rather than admit that a profound change in Scottish attitudes towards Westminster and its parties was going on, the mouthpieces of Cameron and Miliband lapsed into psychobabble. For them, the problem was that Scots, in their hundreds of thousands, had gone mad. They were the irrational victims of an SNP cult, not voters who were only too well informed.

During the six weeks of campaigning, nothing - not a thing - said by Cameron, Miliband and Clegg made an impression on SNP poll numbers. As it turns out, opinion was hardening. The Scots, said London's politicians and press, were "just not listening". I'd venture to suggest there was nothing at all wrong with our hearing. What we hadn't heard too many times before, we didn't care for. Cameron, the Westminster leader with nothing to lose in Scotland, was the only one not to pay the price.

So: 56 SNP MPs; a Labour Party in ruins; the Liberal Democrats left with a single outpost in the Northern Isles thanks to little more than 800 votes; and a United Kingdom that is now less secure than it was before that referendum "settled everything". Yet again, Scots have done more than their share of the work in opposing Conservative government. This time, in fact, fully 50% of voters here chose their party of opposition. But - yet again - England has preferred the Tories.

The claim by Labour in Scotland that a vote for the SNP was somehow the agent of Cameron's victory is as nonsensical now as it was during the campaign. Simple arithmetic proves it: Labour could have won every last one of the seats in Scotland and still fallen short of the Tory total. If Scottish Labour choose to assert, cravenly, that the prospect of SNP influence over Miliband scared English voters towards Cameron they either do not understand what they are saying, or understand well enough and don't care.

If true, what does it mean? That Scottish voters should have declined the choice of a lawful party and declared themselves subordinate to the prejudices of English voters? If that's the case, there's no place for us within the UK. Does it mean, equally, that voters in England will simply not countenance the participation of properly-elected Scottish MPs within a government they regard as theirs alone? If so, the road is the same and it leads in one direction only.

You have a sense that wiser Tory heads understand all of this and are not much disturbed by what it implies. Buffoons understand it, too. On election night, blustering his way back to the Commons, Boris Johnson let it be known that some sort of federal solution would jolly well have to be found to sort out the Scots and restructure the UK.

As ever, Uxbridge's choice for parliament spared us the details. He certainly did not attempt to explain how federalism could ever work when England represents 83.9% of the UK population and Scotland just 8.4%. Others have attempted to deal with that conundrum, one that will come sharply into focus when Cameron attempts his in-out European referendum. What happens, as Sturgeon asked during the campaign, if England votes one way and Scotland, Wales and Northern Ireland vote another? That's the heart of the problem with federalism. When there is disproportion and disagreement, it falls apart.

If federalism cannot be made to work, nothing else remains. Yet what is there of any worth in the Union, in any case, when the political differences between two neighbouring countries are so stark? After five brutal years, no-one in England could have been in any doubt on Thursday about what Cameron represents. The witless austerity programme will continue. Attacks on the poor and disabled will continue. Food banks and Trident missile systems will be countenanced. The Tories are not, if they ever were, an unknown quantity. Yet English voters have given Cameron the majority he could not win in 2010.

A Scot - to be exact, 50% of Scots - can't help but draw an obvious conclusion from that. Sturgeon's offer to voters here and in England during the campaign was also clear. Here was a party of the moderate left proposing an end to Trident and the beginning of the end of austerity; a party prepared to help Labour in "locking the Tories out" and in restoring a little decency to British life. A plurality of voters in English constituencies, it turns out, didn't fancy that. In one way, we should thank them for being so honest.

The 56 SNP MPs cannot expect much help from Labour over the next five years. Miliband has enfeebled his party to an extent that seemed unimaginable just a week ago. Thursday's result was even worse than that achieved by Gordon Brown in 2010. To lose an election is one thing, to lose a shadow chancellor along the way - was that also the SNP's fault? - is abject. Since there is no guarantee that Miliband's successor will continue the attempt to move Labour slightly to the left, however, progressive opposition to the Tories will be difficult. If England desires right-wing politicians, that is what England will be given.

Cameron can recognise the clarity with which Scotland has spoken and come to terms with Sturgeon over the powers due to the Edinburgh parliament, or he can attempt to ignore the SNP 56. The outcome in either event will, one day, be the same. Opinion in England, not all of it classified as right-wing, has grown a little tired of the Scots. We saw it during the referendum and we have seen it again, undisguised, during the campaign. The idea that a Scot can vote for a candidate who might then be declared illegitimate puts all of the arguments in one nutshell.

A non-aligned observer might wonder, in any case, over what estrangement within the Union has done to the politics of Scotland. Look at the landscape now: a sea of SNP yellow on which just three other MPs bob like lonely rafts. We have one of each, as though for balance, but the hard historical truth is that three political traditions, each of them once distinctively Scottish, died on Thursday night. That, rather than the removal of Jim Murphy or the defenestration of Danny Alexander, was the election's real drama.

Half of Scotland's voters chose the SNP; the other half remain to be convinced. A historic achievement by Sturgeon and her colleagues does not alter the fact that another referendum could not be decided on a 50-50 split. Even as Scotland and England diverge, that cause is not yet won, the problem not yet solved. Half of Scotland's voters are not yet persuaded and are now, in essence, without representation in the parliament most of them hold dear. We are in a new world, but it is a strange world.

In this world, suddenly, Labour in Scotland has ceased to matter. A country in which so many were shaped by the traditions and achievements of the party will have to find new ways to understand itself. The voters who destroyed Labour, like the tens of thousands who have joined the SNP since the referendum, once formed its Scottish bedrock. "I didn't leave Labour," they say time and again, "Labour left me." There is a clear and distinct truth in that. But when Sturgeon says her party will speak for Scotland she is claiming to speak, as often as not, for those people.

Still: 56 SNP MPs. No-one, not a soul, thought they would ever see the day, or anything like it. Before the poll, my bet was 48 "give or take". Like half the voters of Scotland, I find myself astonished still by what we have done. There is no doubt that we have spoken, but it is still not clear what we have said about ourselves. So now let's hear what Westminster has to say.