Tony Blair will today be 10 years in office as prime minister of the United Kingdom of Great Britain and Northern Ireland. He is expected to resign soon. Today, too, is the 300th anniversary of the Treaty of Union between England and Scotland in 1707. On Thursday Scottish, Welsh and English voters go to the polls in devolved assembly and local elections. Northern Ireland has already voted and will next week see devolved power-sharing restored.
These elections could bring the Scottish Nationalists to power in Edinburgh for the first time, probably in coalition and pledged to hold a referendum on Scottish independence from the UK. Were they to become Scotland's largest party it would be a difficult legacy indeed for Gordon Brown, Mr Blair's presumed successor. Why should Mr Brown be trusted and supported by middle England voters when he has lost the confidence of his own backyard, it will be asked by Conservative leaders currently enjoying their highest scores in UK polling for many years.
The remarkable coincidence of these facts tells a story of major constitutional, political and electoral change under way in the UK. They explain why Blair and Brown have devoted so much effort in recent months to campaigning in Scotland against the SNP. There is a substantial disenchantment among traditional Labour voters there over Iraq, Britain's Trident nuclear programme and unhappiness with Mr Blair's policies. They add up to a likely swing against Labour this week. Voters know they would not thereby endanger the constitutional settlement because the SNP will not gain an outright majority but will probably have to reach a coalition deal with the Liberal Democrats. In that case any constitutional referendum would include options short of independence. As one Labour insider said of such dealings with the SNP: "It is a case of try before you buy".
This pragmatic streak in Scotland's political culture should caution against any expectation of precipitate change in the UK constitution. Nevertheless, from the Irish perspective it should be recognised clearly that the elements which have given that settlement historical stability can no longer be taken for granted. Mishandled from London, any surge towards Scottish independence has ample scope to tumble out of control - as it could easily do under a Conservative government.
The potential implications for Ireland of such radical developments in the UK are large and curiously under-examined. This is surprising given the imminent installation of the power-sharing executive led by the DUP and Sinn Féin. Mr Blair wants very much to welcome it into being before he goes. He deserves to do so given his extraordinary and indispensable commitment to the Belfast Agreement since 1998. The invitation to Bertie Ahern to address the Westminster parliament recognises how closely the two men have worked together over the last 10 years.