We tend to think of single-party majority government as the norm in Britain. And so it has been in the postwar era. But from 1885, when the single-member constituency became standard, until 1945 such governments were rare – indeed, there were just three, one of which lasted for only a year – the 1906-10 Liberal government, the 1922-23 Law/Baldwin Conservative government and the 1924-29 Baldwin government. Every other government was either a minority administration or a coalition.

Until 1914, the prime reason for this was the return of a solid bloc of Irish nationalists to Westminster – at least 80 in every general election from 1885 to 1910. In 1885, 1892 and from January 1910 the Liberals, the leading party of the left, were dependent on the Irish nationalists for their majority.

The Irish nationalists (who formed the Irish Parliamentary Party), unlike the Scottish National Party and unlike Sinn Fein, which supplanted them in 1918, were not explicitly separatist. They claimed they wished to remain within the United Kingdom and sought no more than home rule – large-scale legislative devolution. But as Charles Stewart Parnell, the IPP’s greatest leader, had put it in 1885, while home rule was the most that could be demanded under the British constitution, “No man has the right to fix the boundary to the march of a nation. No man has the right to say to his country, ‘Thus far shalt thou go and no further’ . . .”

Had it been implemented, therefore, home rule might well have evolved into something like dominion status – independence for Ireland within the Commonwealth – but peacefully, without the repression and civil war that marked the birth of the Irish Free State in 1922.

Home rule, however, required the consent of not just the Commons but also the House of Lords, then composed almost entirely of hereditary peers and with a permanent Conservative majority; and before 1911, the powers of the Lords were unlimited by statute. After the House of Lords had rejected Lloyd George’s “People’s Budget” in 1909, the Liberals decided to reform it, but following the sudden death of Edward VII in May 1910 they sought a “truce of God”, a compromise with the Conservatives.

The two parties came together in a constitutional conference, which sat from June to November 1910. This conference attempted to distinguish between different categories of legislation – ordinary, financial and constitutional – proposing different procedures for each and with the powers of each house to be laid out in statute. Use of the referendum was also discussed. The conference was attempting, in fact, nothing less than the production of a written constitution for Britain.

Not surprisingly, perhaps, it broke down, primarily because the parties could not agree to which legislative category home rule belonged and whether special procedures were needed to implement it. Instead of an agreed solution, therefore, the Lib­erals, prodded by the nationalists, decided to replace the absolute veto of the Lords with a suspensory veto of two sessions – reduced to one session in 1949 by the Attlee government.

During the constitutional conference, Lloyd George, the Liberal chancellor of the Exchequer, made a startling proposal – nothing less than a Liberal/Conservative coalition, which would impose on both Irish nationalists and unionists a system of “home rule all round”, a quasi-federal solution for the whole of the United Kingdom. If the Irish demurred, then (so Lloyd George predicted), the Liberals would “wash their hands of the whole affair and leave the Irish to stew in their own juice”. But the coalition proposal got nowhere; nor did home rule all round. It involved pulling up the British constitution by its roots to solve the Irish problem and imposing upon England a form of government it did not want purely to satisfy the Irish nationalists.

Once the Irish left Westminster in 1918, declaring their independence and setting up their own parliament in Dublin, pressures for constitutional reform faded away. “The two supreme services which Ireland has rendered Britain,” Winston Churchill wrote mischievously in 1929, “are her acces­sion to the Allied cause on the outbreak of the Great War, and her withdrawal from the House of Commons at its close.”

The SNP has now resurrected the constitutional debate. The Scottish Nationalists, could well, after next month’s general election, exert a stranglehold over British politics similar to that of the Irish nationalists in 1910. But whatever the outcome, the Scottish Question and the English Question will come to the fore.

A second Conservative/Liberal Democrat coalition or a Conservative majority government will lack, as the 2010 coalition lacked, legitimacy in Scotland. Scotland will once again have a government it did not vote for. A government of the left, by contrast, will almost certainly lack a majority in England, and the issue of “English votes for English laws” will be raised with even greater intensity. Either way the Union will again come under threat.

As in 1910, there are many who suggest a federal solution. But that implies some similarity between the wants and desires of all four parts of the UK and the imposition of a new and probably unwanted system of government in England purely to accommodate the Scots. Plus ça change.

Kenneth Baker, the former Conservative education secretary, has suggested another way out of the deadlock – a grand coalition of the Conservative and Labour Parties that might, as was hoped in 1910, impose a solution to Britain’s constitutional problems. Yet that, too, is an unlikely development.

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The 2015 general election, then, is likely to raise a question mark over the very future of the UK. But the difficulty we face in confronting our constitutional problems is that they are interconnected. The Scottish Question is intertwined not only with the English Question but also with the question of whether Britain remains in the EU, and with the electoral system. It would in fact be easier to resolve the Scottish Question, were there to be electoral reform.

In the 2010 election, the Conservatives won just one seat in Scotland. Yet they won one in six of the votes – around 17 per cent; just 3 percentage points fewer than the SNP – while Labour won 41 of Scotland’s 59 constituencies on just 42 per cent of the Scottish vote. A proportional system would have given Labour 24 seats and the Conservatives ten. In May, the SNP could make a clean sweep in Scotland on less than 50 per cent of the vote. First-past-the post makes Britain appear more divided than it really is and exacerbates the West Lothian problem because it exaggerates the imbalance in strength in Scotland between Labour and the Conservatives. First-past-the-post therefore threatens the unity of the country. Proportional representation, by contrast, would alter the dynamics of the conflict between England and Scotland and make it more manageable.

Resolving the English Question is also intertwined with other constitutional questions, and in particular with the status and reform of local government. George Osborne’s commendable attempt at devo-max to Greater Manchester requires, if it is to be successful, the devolution of real taxing powers to local government and of ministerial powers over such matters as health. But above all, a successful policy of devolution and decentralisation requires a clear understanding of what matters are fundamental to the UK as a whole – what are the basic constitutional, social and economic rights that should be enjoyed by every citizen – and what matters are capable of different treatment in different parts of the UK. That understanding is best embodied in a written constitution.

It is indeed because our constitutional problems are so interconnected that there is so strong a case for a constitutional convention. Speaking in Edinburgh in 2013, Douglas Alexander, the shadow foreign secretary, called for a Scottish convention to consider the future of the Scottish constitution, similar to that of the convention of 1989 which paved the way for devolution. But the future of Scotland should not be seen in isolation from that of the rest of the UK; nor can further devolution be considered in isolation from such matters as reform of local government and electoral reform. What is needed is a UK-wide convention, with popular participation, to consider the constitution as a whole.

In 1910, the crisis of the constitution was resolved in an ad hoc manner and the chance for a real constitutional settlement was missed. Will the same happen in 2015? Or are we, on the 800th anniversary of Magna Carta, approaching a genuine constitutional moment?

If we are, as I believe, approaching such a moment, it is because our constitutional problems have not arisen in a vacuum but reflect real pressures of social change – in particular, the end of deference and the breakdown of old class and party loyalties. There is a growing conflict between new social forces and our traditional constitutional forms. It is becoming increasingly clear that these constitutional forms are relics of a past era. Our political system needs to become more congruent with the public philosophy of what David Cameron has called a post-bureaucratic age, whose watchword is fluidity and whose leitmotif is a politics of openness and transparency. This means publicly stated constitutional rules rather than the tacit understandings that have hitherto served us as a substitute for a constitution.

The democratic spirit in Britain is not unhealthy. The Scottish referendum showed that there is a huge reservoir of civic potential that the political parties have largely failed to tap. It is the institutions and the mechanisms which seek to represent the democratic spirit that are at fault. Disenchantment with politics flows from the conflict between a maturing democracy, in which voters are accustomed to wider choices than in the past, and a political system that still bears all too many of the characteristics of a closed shop.

The task now is to funnel the democratic spirit down constructive channels so that crisis can be transformed into opportunity. That is the fundamental case for a constitutional convention and, if it comes about, it will repay a debt of gratitude that we owe to the Scots for voting to stay within the UK.

Vernon Bogdanor is professor of government at King’s College London. His pamphlet “The Crisis of the Constitution” has just been published by the Constitution Society