The Commons Speaker John Bercow and invited guests will tomorrow mark the centenary of the Third Irish Home Rule Act.
On one level it's a curious commemoration, for third-time-lucky didn't apply when it came to answering the Irish Question. With the outbreak of war in August 1914, although the Government of Ireland Act reached the statute books on, of all dates, September 18, 1914, it was postponed for the duration of the conflict.
But even when the armistice came it had been overtaken by events, the Great War having hardened moderate Home Rule opinion into vehement support for the real deal. It's become one of the great "what ifs" of British political history - what if the UK had successfully established a devolved legislature in Dublin?
And what if, as some envisaged, the Act had paved the way for a federal UK? Indeed, even as Ireland's constitutional ambitions turned violent, a sub-committee of the British Cabinet was charged with considering just that. Ultimately it applied only to Ireland, and even that half-measure proved stillborn.
Recently there's been much talk of a federal solution to the Scottish Question, as indeed there usually is when the SNP is breathing down Westminster's neck. At Glasgow University late last week the Conservative MSP Murdo Fraser cogently set out the case, while earlier this month former PM Gordon Brown advocated a federal UK in all but name.
The "f" word also punctuation contributions to a debate in the Upper House last Tuesday. Lord Stevenson urged ministers to "seize the legislative moment", Lord Morris (the architect of Welsh devolution) talked of looking "radically at federalism for all the countries of the United Kingdom", Lord Judd said "a federal United Kingdom is what is required" while Lord Richard (a former Leader of the Lords) simply declared "something has to be done".
That something was a federal UK, and of course it would be a pretty big something, so big many Nationalists now disparage federalism in terms not unlike those used to rubbish their goal of independence not so long ago. Without actually attacking the principle of federalism, it is nevertheless dismissed as unworkable, lacking demand and even, in the words of SNP MSP Stuart McMillan, "pie in the sky".
It's a curiously conservative critique, particularly coming from self-styled constitutional radicals, and one that's been applied to every major social and political advance of the last century or so. Independence, with all its difficulties and contradictions, is presented as eminently achievable while a federal UK is dismissed as a Liberal pipe-dream. Yet what critics conveniently miss is the fact the UK has, since the late 1990s, already become a quasi-federal state in which old assumptions about "sovereignty" and British constitutionalism have been constantly revised. Just as the old Stormont parliament enjoyed a federal relationship with Westminster, so too do the assemblies and parliaments of London, Wales, Northern Ireland and Scotland. Perhaps it could be called federalism by stealth, and so stealthy a lot of people don't appear to have noticed.
More to the point, that quasi-federalism can only strengthen as more power is devolved to London, Cardiff, Belfast, Edinburgh and - as Ed Miliband will set out this week - to city and county regions in England, the traditional elephant in the room for federalists, though far from an immovable one.
In yesterday's Sunday Herald Iain Macwhirter fleshed out the standard rebuttal to what he called federalist "nonsense" (though he himself is, in theory, sympathetic), chiefly that there isn't "a cat in hell's chance" of the UK introducing federalism. But Macwhirter, like others, is prone to caricaturing the argument in order to dismiss it.
Thus it follows there's "no demand for federalism in England", even though several comprehensive surveys of English public opinion have indicated increasing levels of discontent with the status quo and a near consensus among "civic" England that greater devolution for the cities and regions is the way forward. It might be hard to detect from within the referendum bubble, but the long-neglected English Question becomes ever more potent.
The usual straw man of an "English parliament" has also been assembled, even though not a single federalist is advocating any such thing (only the historian Linda Colley has mooted an all-England assembly sitting in York). When it comes to proposals for a reconstituted Upper House representing the nations and regions of the UK, however, the cynics are on firmer ground.
Although their Lordships' enthusiasm early last week was welcome, they represent a huge barrier to federal reform, for not only are there more than 800 vested interests reluctant to sacrifice their ermine, but also hundreds of prospective vested interests (step forward party donors and retiring MPs) similarly reluctant to close down their legislative retirement home.
Nevertheless, a reformed House of Lords would be essential, for there isn't a federal country in the world that doesn't use its upper house as a territorial balancing mechanism. This, as Canada demonstrates, doesn't necessarily have to be elected or strictly apportioned as in the United States. Labour seems prepared to give it a go with a senate proposal, as The Herald recently revealed, likely to form part of its next manifesto.
Whether that progresses any further than previous efforts depends in large part upon political will, but as Lord Richard pointed out last week the "West Lothian and Merthyr Tydfil questions are not going to go away"; indeed, "they are going to be joined by the Marylebone conundrum", especially if Boris Johnson succeeds in his quest to grant his fiefdom greater fiscal autonomy. Passing through Edinburgh on Friday Ed Miliband dodged a legitimate question along these lines, particularly given his restated commitment to "more powers" should be become Prime Minister. He simply said he had "no plans to create two classes of MP", but the only convincing means of squaring that circle is via federalism. Otherwise, as the commentator Alex Massie memorably remarked, you end up with the "West Lothian Question on steroids".
Part of the challenge isn't purely logistical. As Adam Fusco of York University argues in the latest edition of Renewal, viewed as "a form of radical self-government", federalism could "reconcile the British left with the principle that underpins the drive for Scottish self-determination", leaving social democratic policy goals "up for grabs" in the process.
But however challenging, federalism is eminently achievable. The UK has been devolving power - administratively and legislatively - for more than a century, so the idea federalism is beyond its competence doesn't stack up. To paraphrase the late John Mackintosh, people across the UK want a degree of government for themselves and it isn't beyond the wit of man to devise the institutions to meet those demands.
Writing in the New Statesman last year, former Labour MP David Marquand viewed things, aptly enough given tomorrow's anniversary, through the prism of Ireland a century ago. "Does the UK become a federal state, or does it break up?" he asked rhetorically. "It would be nice to think we shall do better than our great-grandparents did." Amen to that.