The Yes movement has been set a challenge - are we ready to step up?

Her speech from Bute House was generous, engaging and at times, almost philosophical in its consideration of the decisions a leader must eventually make about their role.

She may or may not be right that in time, leaders become not the enablers of change but the barriers to it and that in our current politics, entrenched views can only be shifted by dramatic renewal. Yet, of course, I wish she hadn’t chosen to go now.

But she has, and as a party and a nation, we must respect that decision.

Naturally, she leaves a huge legacy already.

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I first met her, ironically enough, at the Salmond For Leader campaign back in 1990. Over the next nine years, before the Scottish Parliament came into being, she played a variety of roles in the SNP which helped to make the party’s message credible and improve organisation on the ground.

She was a dynamic health secretary, her time as infrastructure secretary brought some new coherence to public investment, and her contribution to making the independence case through the White Paper was unique. It would not have happened without her.

As First Minister, she ensured the delivery of better services, improved the quality of life for those most in need, oversaw the start of Scotland’s ethical and effective benefits system and tried to defend the Scottish Parliament and people against the worst effects of Brexit and the growing impositions from Westminster.

Of course, most notably of all, she visibly and determinedly led the nation through the pandemic in a way that was selflessly focused on physical and economic safety and survival whilst simultaneously having to defend herself against attacks from former friends.

She found that particularly hard, I know.

She has never wavered on independence, but she has constantly thought about – and discussed with others – how best to ensure that the next big moment of decision on Scotland’s constitutional future was not only deliverable but resulted in the Yes vote that Scotland needs. That alone is no small thing to carry.

In time, all these matters and many more will be studied, poured over and analysed but yesterday for me – and I suspect for some others who have known her a long time – none of these things were as noticeable as, in the midst of our shock, the sudden flashes of her distinctive, off-the-cuff, mischievous humour.

There has been too little of that in recent times, but now it seemed to say the old Nicola is coming back.

Whilst Nicola as leader will be sorely missed, Nicola as friend and colleague still has a vast amount to give to Scotland and the cause.

No longer having an office two doors down from hers, I haven’t seen her face to face as much as I used to but when we have spoken – in person or on the phone – I have been more than aware of the massive weight on her shoulders.

We all knew that could not be borne forever.

In my column in this newspaper just last week, I wrote of her as someone who is “decisive, principled and talented”, with strong opinions who works tirelessly for her fellow citizens.

She is all that, but she is also more than that. She is a very private human being who values the company and support of her family above all else. It is therefore scarcely remarkable that the nature of modern media-driven confrontational politics – “brutal” she rightly called it yesterday – has, in the end, played at least some part in deciding to be done with a role which takes over your life and overshadows or intrudes into every action and relationship.

Jacinda Ardern called her feeling before resignation “running on empty” and she was fuelled by the same sort of spirit as Nicola.

Inspirational national leadership is a rare mix of talent, determination, intelligence, intuition, imagination, and charisma. It is, alas, even more difficult to acquire and exercise for women, given the still misogynistic nature of much of our politics and media and is constantly drained by people who have never possessed a drop of these qualities themselves.

Douglas Ross’s graceless and bitter statement on the resignation was no more than one would have expected from one of the most graceless and bitter politicians in Scotland. He is a small man in every sense, but bitter and graceless words also came from some journalists who should hold themselves at least partially responsible for the deliberate demonisation of her and her party. They won’t but will instead – as we have seen this past weekend – clutch their pearls in huffed offence and astonishment at the very thought.

But Nicola also talked of something much more important yesterday which rises above all the noise and, it is to be hoped, will speak directly to Scotland.

It is nothing less than an appeal to reset the politics of our country and to endeavour to have debates on vital issues – including, most vitally of all, our national independence and the doors it will open to the world – which do not degenerate into disparagement and entrenched dislike.

That is a message to her party, to the movement of which it is part, to those who disagree with the constitutional and political journey that she led and to those who report and comment on it.

The question is: Are all those parts of our national life ready to take up the challenge?

Of course, even if we were all to sign on to such an idea, it would take time for its effect to percolate through. But that doesn’t mean we shouldn’t try, and the first step will be to ensure that there is an internal debate within the SNP about the future which is respectful, open, constructive and focused on the steps to take to secure the Scottish people’s right to choose the form of government best suited to their needs.

I remain of the view that if the referendum road is blocked, another road must be found and like Nicola, I think that a Westminster election is the best – though not the perfect or only – option.

But before we take that decision, we need to elect a new leader.

The SNP constitution defines the role of that leader as being to set the political direction of the party, lead elections and other campaigns, approve manifestos for parliamentary elections and articulate the argument for an independent Scotland. All of those roles come into play when considering a plebiscite election and the necessary renewal of the independence campaign, focused on the benefits of Scotland becoming an independent country and a full member of the EU.

The SNP, therefore, need to find in their ranks – much larger at every level now than they were during the last contested leadership election in 2004 – the person who can best do that for Scotland as it is now.

Nicola outlined yesterday what pressures said candidate will face and the strength of character they will need to take on the role and accept that there is no respite from it until it is laid down again.

Yet she also suggested ways in which that role might be exercised to heal divisions and to seek out consensus. She was hopeful that the advantages of a fresh start could be utilised not just by the SNP but also by the whole national movement and by the opposition parties. Perhaps even those parts of the media which were still grubbing about in the gutter yesterday could be persuaded to set their sights a little higher and contribute to improving the context for collaborative decision-making by the entire realm of Scotland.

I regard Nicola as a good friend, and I greatly admire her but I have had my differences with her too.

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The leadership contest of 2004 was a difficult one, and 10 years on, she found no place for me in her first cabinet.

But politics is about keeping going. It is about being faithful to a cause that is bigger than any individual and about loyalty to colleagues even though you disagree with them.

The learning experience it presents is how best to do such things, particularly in adversity.

Yesterday was, whilst unexpected, not unpredictable. At some stage, the guard always has to change, and a new political generation has to point the way ahead.

That is not an easy thing for any party to accept, particularly if they have been led for an extended period by someone so dedicated and determined as Nicola.

Yet now is the moment and without doubt, out there is the person who can usher in the next and final step to independence.

So let’s choose that person, and keep moving forward.