ON Wednesday night something rather wonderful started to happen. Across the UK people began signing an official online petition calling on the UK Government to revoke the Article 50 notice and allow the UK to remain in the EU.

They have continued to do so at such a rate that the site has repeatedly crashed under the weight of traffic. At the time of writing it has been signed by well over four million people.

In the House of Commons on Thursday morning my colleague Marion Fellows drew the petition to the attention of the Leader of the House of Commons, Andrea Leadsom.

Clearly stung, she replied that should the petition reach more than 17.4 million signatures, there would be a very clear case for the Government taking action.

She may live to regret those words.

Revocation would not be an option but for the litigation which I pursued with Andy Wightman (pictured below), Ross Greer, Alyn Smith, Catherine Stihler and David Martin. We, in turn, owe a huge debt of gratitude towards Jo Maugham QC who drove the litigation forward, our legal team, the Good Law Project who organised the crowd funder and all those who contributed.

On December 10 2018 the Court of Justice of the European Union ruled that the UK could revoke the Article 50 notice and that it could do so unilaterally, without the necessity of the other member states’ consent. At the time, for reasons which are not entirely clear, the ruling was largely ignored by the mainstream media.

However, in the past few days as the constitutional crisis which the PM has created has grown everyone is now talking about revocation as a real possibility.

I am very proud to be part of the team which went through a year of court hearings and risked substantial expense to get the crucial ruling. I am particularly proud to have been the only MP prepared to stay the course because, at the end of the day, the presence of an MP on the team proved vital to persuading the Court of Session in Edinburgh to refer the case to Luxembourg for a ruling.

Jo Maugham has already spoken about the pressure brought to bear upon him not to pursue the litigation by some in the political establishment. When I was deciding whether to join in the case I experienced similar pressure from some surprising quarters, but I am glad I resisted it and trusted my instinct that this was something that could yet become very important to Scotland and the UK.

The turning point for the case came with Dominic Grieve’s amendment which resulted in Section 13 of the EU Withdrawal Act stipulating that MPs must have a meaningful vote on the final deal. This meant that when MPs came to take that vote they needed to know whether there was an alternative to accepting the deal or triggering no deal i.e. revocation.

This was what persuaded the Scottish judges to refer the case to Luxembourg, because they accepted that at the very least MPs needed to know the answer to the question which, in the light of the requirement for a meaningful vote, was not a hypothetical question, as the UK Government had argued.

At our conference last October the SNP became the first major political party to wholeheartedly embrace a second EU referendum as a way out of the mess the Tories have created. However, a People’s Vote with the option of Remain would be pointless unless it was possible to revoke Article 50.

Yesterday, together with Nicola Sturgeon and Ian Blackford, I joined the People's Vote rally in London. We marched alongside fellow Scottish and Welsh nationalists and progressive elements from across the UK. Before the march started I addressed the LGBT rally for a People's Vote and went to meet with some of the huge contingent of people who had travelled down from the Scotland for the march.

The atmosphere at the march was really quite electric. It was interesting how far away people had come from ... all over the UK and from the EU. It was a really sort of positive vibrant atmosphere.

I went on the march because I think it’s really important for the SNP to continue to be at the forefront of the fight against Brexit and be part of the growing movement that recognises revoking Article 50 is a real possibility. The events of the past few days have really made it possible again for those of us who don’t think that Brexit is the right thing to do to believe that it can be stopped.

I have no doubt that some of my fellow Yessers will ask why I wasn’t at the pro-indy rally in Glasgow yesterday instead. The answer to that question is simple. Yesterday we were marching to persuade the UK Parliament that the issue of whether the whole of the UK should remain in the EU should be put back to public vote.

I don’t need to march to persuade the Scottish Parliament that there should be a second independence referendum because they are already persuaded of that. In March 2017 by a majority of 69 to 59 Holyrood voted to hold another independence referendum and it is quite clear from Patrick Harvie’s comments at FMQs last week that the pro-indy majority still exists in the Scottish parliament.

Brexit, with or without a deal will damage the Scottish economy and cost jobs. The majority of voters in Scotland want to remain and it is the SNP’s job to do all it can to respect their wishes and protect Scotland from an economic disaster. If Scotland was already an independent country our foreign policy, like Ireland’s, would be to try to keep England as close to the single market and customs union as possible, because that is in our economic and social interests.

Those who support independence for Scotland should not hesitate to support the campaign to revoke Article 50 or a second EU referendum for fear that stopping Brexit will undermine the case for Scottish independence. The arguments for Scottish independence existed and were strong before Brexit was ever a reality and they have been emphasised by the treatment of Scotland and her parliament during the Brexit process. The stark contrast between Ireland’s treatment within the EU and Scotland’s treatment within the UK amply illustrates that, unlike the EU, the UK is not the union of equals described by Better Together in 2014. Brexit has also very clearly demonstrated the democratic deficit experienced by Scotland within the UK and the limits of devolution.

The manifesto on which the SNP won the 2016 Holyrood election read as follows (at page 23): “We believe the Scottish parliament should have the right to hold another referendum if there is clear and sustained evidence that independence has become the preferred option of a majority of the Scottish people – or if there is a significant and material change in the circumstances that prevailed in 2014, such as Scotland being taken out of the EU against our will.”

It is clear therefore that the mandate for a second independence referendum persists even if Brexit does not happen. No one could seriously argue that what has happened over the past three years is not a "significant and material change of circumstances”.

When and how we go about holding another referendum is a matter of tactics for the First Minister. The why is for all of us who live in Scotland and that is why I am so keen to pursue setting up Citizens Assemblies through the resolution I have proposed to SNP conference so that people from across Scottish society can participate in building the vision of an independent Scotland. Like most people I look forward to the announcement of the FM on the timetable for indyref2 which last week Ian Blackford told us was imminent. It was the right decision for the FM to top the bill at the march yesterday. Just as it was the right decision for the Scottish Six to establish the right to revoke Article 50.

Theresa May has sought to marginalise Scotland throughout the Brexit process, so it is indeed a rich irony that Scottish Parliamentarians and the Scottish courts have offered the UK the lifeline it needs to escape the mess she has created. I am sure this will be remembered across Europe when an independent Scotland looks to take her rightful place at Europe’s top table. It should also be borne in mind by politicians from unionist parties. Scotland has led the fight against Brexit, in return we must be given the right to determine our constitutional future in accordance with law.