I WAS washing the dishes absentmindedly with radio on in the background when the teatime news delivered what is potentially one of the most important –and explosive – developments for Scots since we were voted out of the European Union against our will in the summer.

As is often the way, the information in question was tagged on to another item – in this case Tony Blair’s latest intervention on Brexit – and disguised as a mere afterthought. But my ears pricked up immediately when the newsreader mentioned that Lord Advocate James Wolffe had published the submissions he will argue on behalf of the Scottish Government at the Supreme Court next month in a bid to secure a vote for Holyrood as well as the House of Commons on the triggering of Article 50, the process needed to formally invoke Brexit.

Legal wrangling rarely makes for the sexy news, of course. But make no mistake, this is big. Very big. Indeed, it potentially sets up a stand-off that would dwarf even Theresa May’s forthcoming gunfight at the EU coral in terms of importance, at least for the future of the UK. Why? Because if given a vote on article 50, it is likely that Holyrood - unlike Westminster - would deny the UK Government permission to start the process. In effect, it would veto Brexit. And where does that leave the already fragile UK constitution? Pretty goosed, I’d say.

Think about it. Were Scotland, the junior partner in the Union, to veto the express wishes of England to leave the EU, then the toxicity we’ve seen down south over the last six months would ramp up times a thousand. To paraphrase Mr Churchill, up with this the Brexiters simply could not put; public opinion in England could turn very nasty indeed. Brexit has significantly widened the existing gulf between Scotland and England, and it’s interesting to note that in recent public discourse any initial reticence by either side to talk of “them” and “us” - Scottish and English, Brexiters and Remainers - has all but disappeared since June: the gloves are well and truly off.

And that makes the positions of the governments in Edinburgh and London challenging at best, untenable at worst. If she still wanted to forge ahead with Brexit following a Holyrood veto of Brexit, Mrs May would surely be forced into rewriting Britain’s unwritten constitution and creating the sort of federal Britain her party, and indeed Labour, have always stood firmly against. In turn, federalism would surely make the case for full independence less palpable; and although in some ways such an arrangement might suit First Minister Nicola Sturgeon, it is unlikely to agree with many in the indyref2-hungry new SNP membership.

So, with such potentially complex and explosive consequences, is Ms Sturgeon right to plough ahead with this legal challenge in the Supreme Court at all? You bet she is. Indeed, with so much at stake for Scotland economically as well as politically and constitutionally, this may well turn out to be her most important move so far as first minister.

Therein lies the rub with a hard Brexit, you see: unintended consequences. And for Scotland these could be genuinely frightening in that they not only impact upon the hard won devolution of the last 20 years, but also potentially create the need to roll it back.

This position was made clear in these pages only last week by Scottish EU law expert Alastair MacIver of Tilburg University in the Netherlands. Mr MacIver eloquently outlined how the creation of a UK single market in the wake of withdrawal from the EU single market would in practice require Westminster to take back many of powers currently devolved to Holyrood. Single markets require clear and unbending rules, you see. And who would write the rules for a UK single market? Westminster, of course. Under such an arrangement Edinburgh would also miss out on any new powers repatriated from Brussels.

But you won’t hear either side of the Scottish independence debate talking about these consequences, precisely because they are so hideously unpalatable.

All this is at the heart of the Lord Advocate’s submissions. It goes, after all, to the very crux of what Brexit means for Scotland. And with this in mind it’s time for people on both sides of the indy debate to stand together and defend devolution to the death. After all, if the UK Government is prepared to take Scotland out of the EU without allowing our devolved parliament to make its voice heard, then what does that say about the integrity of the devolution settlement in the first place? What would it actually be worth? The term, I believe, is sweet Fanny Adams.