The Scottish independence referendum established many of the conditions that led to Labour’s catastrophic 2015 general election defeat. In the process it also illustrated three fundamental truths now shaping politics in Britain.

The first truth is that there is still a huge market for big political ideas; these ideas don’t come much bigger than breaking up the United Kingdom. The second is that it has never been harder to communicate a simple, popular, progressive political platform. The third, of particular relevance to the Labour Party, is the need to expect and prepare for the unexpected.

In the run-up to the referendum ballot, Gordon Brown regularly explained to anyone prepared to listen that the ‘No’ campaign would win the poll, but that a sizeable ‘Yes’ vote would extract revenge for its defeat on the Labour Party at the next general election.

Labour should have been prepared for the beating it took in Scotland, but a combination of ignorance, arrogance and a misplaced intellectual snobbery that lent itself to some truly appalling political judgments, meant that the party walked headlong into an avoidable disaster.

For the sake of the Labour Party – and every person and community for which it exists to serve – these lessons must now be learned.

It is no longer unthinkable for anyone to imagine the disintegration of the United Kingdom – this may even be likely – so Labour must now prepare for life in a country without Scottish Labour voters.

Welcome onto the stage yet again, the issue of the realignment of the English Left. This may be a tired canard, but in terms of principle and practicality, this looks increasingly necessary. This realignment could take a number of forms; the adoption of a federal party structure for the Labour Party, including the creation of English Labour to sit alongside Welsh Labour is something that the party should now consider in any event. But a more profound, all encompassing re-alignment would pursue a comprehensive merger between Labour and the Liberal Democrats.

No longer the effete fancy of Jenkins, Blair and Ashdown, a United Kingdom without Scotland would demand such a realignment in order for England to secure the kind of progressive government needed all over England and Wales. These decisions are upon us and they cannot be wished away. It would be a tragedy for progressive politics in England particularly if the need for such change was now foolishly ignored out of hand. The next leaders of Labour and the Liberal Democrats must recognise that the unthinkable is now normal and that business as usual will likely result in permanent irrelevance. Change or die; this is the brutal truth.

Writing in this publication before the general election, Professor Richard Grayson wrote of the creation of a possible Labour-Liberal coalition in the event of a hung parliament. The choice facing Labour in these circumstances, he wrote, was “how it can best represent the people whom only it represents…”

By definition, an identical choice would have faced the Liberal Democrats and this logic must now be applied to a future disunited Kingdom without a progressive Scottish bloc. Partisan tribalism – naturally – could kill such notions. For many, the purity of irrelevance and opposition will always remain preferable to the compromises and pragmatism necessary to securing power. For Labour and the Liberal Democrats, read the Montagues and Capulets- the ancient blood feud may yet deprive each of the objects of their love. That object? A progressive England.

George Eaton, again in the pages of this publication, reported on the joint report commissioned by the Fabian Society and the liberal think-tank Centre Forum entitled ‘Common Ground’. The report highlighted those many areas where Labour and Lib Dem policies were almost identical, but the conclusion of the report noted, “It will be politics, rather than the policies of the two parties, that will decide whether a partnership is possible.”

True enough and the politics are now clear. The Conservatives won the last election in large part because it successfully pitted England against Scotland and sold the lie that only the Tories would represent England. No matter what offence this caused to Progressives of all parties in England, this lie suits the SNP just fine.

It may or may not be too late to save the Union. In any event, England is home to a strong progressive tradition that its two major progressive parties should work to unite, not divide. Labour must learn the lessons of Scotland: it’s time to think the unthinkable.