TOMORROW marks 20 years to the day since the referendum result which heralded a new era of Scottish democracy.

That day the people voted overwhelmingly for a Scottish Parliament, to take responsibility of a whole range of policy areas affecting their everyday lives.

It was the Earl of Seafield who famously remarked at the end of proceedings in the old Scottish Parliament in 1707: “Now there’s ane end of ane auld sang.”

Thankfully, the song was merely being held on pause. The people’s choice on September 11th 1997 meant it could be sung again – allowing my colleague Winnie Ewing to remark, perhaps equally famously as MSPs took their seats for the first time two years later, that “the Scottish Parliament, adjourned on the 25th day of March in the year 1707, is hereby reconvened”.

The importance of the 1997 referendum simply cannot be overstated. It was, as the historian Sir Tom Devine has observed, the biggest development in Scottish political life since the Treaty of Union.

Tomorrow, I will deliver a speech in Edinburgh reflecting on the anniversary of the vote and what it means, but more particularly looking forward at how the parliament can better serve the people in the years and decades to come.

And it is an opportune moment to do so – not just because of the significance of the date.

That is because the Scottish Parliament, and the entire foundations of the devolution settlement on which it is based, now faces its biggest challenge since it received such a decisive democratic mandate 20 years ago.

The UK Government’s Brexit proposals – through the proposed EU Withdrawal Bill – constitute a blatant power grab which, far from enhancing the powers of the Scottish Parliament as has been claimed, would throw the process of devolution into reverse for the first time in two decades.

The bill as drafted contains provisions for the wholesale transfer of powers from Brussels to Whitehall and Westminster – including in devolved policy areas such as farming and fishing.

Conservative ministers attempt to downplay this by claiming, somewhat unconvincingly, that their intention would then be to re-devolve powers – but only some and only those which they saw fit to.

That approach utterly demolishes the principle outlined by the late Donald Dewar in framing Holyrood’s remit, which made clear that all powers were to be transferred to Edinburgh other than those explicitly reserved to Westminster.

The Tories’ Brexit proposals, by suggesting that devolved powers which are currently exercised at European level should be repatriated to London and not Scotland, ignore that principle. Indeed they breach it, meaning that the founding basis of the Scottish Parliament, endorsed in a nationwide democratic vote, would be eroded.

The further effect of the Conservatives’ approach is that if powers over things like agriculture are not repatriated from Brussels to Scotland and the other devolved governments – as they should be – then it will prevent Scottish ministers from making any changes to current EU law in these areas, while Westminster will be able to change the law for England.

I have made clear that – as currently drafted – it is inconceivable that the Scottish Government would recommend to MSPs that they should give legislative consent to the EU Withdrawal Bill.

It is up to UK ministers to recognise that, and to make the appropriate changes to the draft bill which would protect the existing devolution settlement.

The Scottish Government is not alone in our view. Carwyn Jones, the Labour First Minister of Wales, has made clear his government shares our position.

And there is also wider recognition of the threat to devolved principles. The Law Society of Scotland last week commented that: “The effect of the bill would be to remove the legislative competence of the Scottish Parliament in relation to any matter in retained EU law. This would be the case even if it related to areas of law not reserved to the UK under the Scotland Act, such as agriculture or fisheries.”

And the House of Commons itself has also produced its own paper on the subject, which similarly observes: “The Bill effectively re-reserves to the UK Parliament these areas of competence, within competences which have otherwise been devolved.”

That is the stark reality now facing us, two decades on from the vote which re-established a Scottish Parliament.

The UK Government’s Brexit proposals are also facing a challenge from those south of the border who warn that there is a parallel power grab underway in the manner in which UK ministers are seeking to use centuries-old convention to concentrate overweening executive power.

Tomorrow is a day to quietly celebrate a landmark in Scottish democracy – but it should also mark the start of concerted, cross-party efforts to defend our Parliament.