The figure of Alex Salmond dominated the Scottish independence referendum, much as he has dominated the country’s political landscape for the past seven years.

So his resignation following the defeat of his bid to establish Scotland as an independent country, is a development of enormous significance and some surprise.

With the dust still settling from the lost vote, he announced on Friday afternoon that he intends to step down as First Minister and leader of the SNP. After citing the vote and negotiations now due to take place with Westminster, Salmond told invited journalists:

For me right now, therefore there is a decision as to who is best placed to lead this process forward politically. I believe that in this new exciting situation, redolent with possibility, party, parliament and country would benefit from new leadership. After the membership ballot I will stand down as First Minister to allow the new leader to be elected by due Parliamentary process.

It is a move that will stun and surprise the world of Scottish politics. And there will be speculation about how long he has known he might take such a course of action.

His political opponents may label him everything from “driven” to “smug” but among them a common theme is that Alex Salmond is intensely private; a man “difficult to know”, and about whose private life very little is known. Many in Scotland could probably not confirm if he is even married. He is, although his wife Moira is 17 years older than him, they have no children, and she rarely appears in public. He likes the horses and gambles on races, likes his golf too, and knows his history. He is considered a natural politician by many, although some dismiss him as cold and calculating, but he is certainly the face of Scottish nationalism today.

When Alex Salmond became active in politics while studying economics and medieval Scottish history at St Andrews university in the early 1970s, it was a conservative institution, and the SNP had remained a fringe party for most of the period since its formation in 1934. Yet it was to the SNP Salmond immediately flocked, becoming vocal, very active, and honing his skills for the future.

Interestingly, the story of how he came to join the SNP illustrates his propensity for controlling his public image. It is habitually said that he did so after an argument with his Labour-supporting English girlfriend, although his biographer, David Torrance, notes that this story is “not exactly solid”. Whatever the impetus, his passion for the nationalist cause has remained strong; strong enough to fuel a constitutional revolution in a country where such things just don’t happen.

After leaving university Salmond worked as an economist for the government and then the Royal Bank of Scotland but remained active in the SNP. As the party went through turmoil in the late 1970s, as the first fight for a Scottish legislature was fought and lost, he became a leading figure in the “79 group”, advocating a more active, left-wing approach. This led to him being expelled, briefly, in 1982.

Returning a few months later, he would be elected to the Westminster parliament in 1987, and leading the party within three years. After devolution he retired as leader, only to return in 2004 after the party suffered losses in the Scottish elections. Nor did it take him long to turn the party around, becoming the first minister of Scotland in 2007, and leading the SNP to form the first majority Scottish government in 2011.

This journey from expelled rebel to triumphant leader only illustrates his political capacity for winning battles others might abandon or avoid. In a few short years he first brought an end to internal feuding within the SNP, then united the party behind a more gradualist approach, leading it to supporting a less idealistic form of independence within the EU. His tenacity is clearly effective.

Yet he is often criticised for that tenacity. It has been claimed that there is no “lightness of touch” in his debate. Considered a skilled debater, he is fierce and relentless, but perhaps better in the rough and tumble of the parliamentary chamber than in the light of a TV studio. After performing badly in the first head-to-head debate in the referendum campaign he returned to what many see as a solid win against Alistair Darling, leader of the Better Together campaign.

Salmond never actually achieved the knockout blow many expected. All the same, he took the SNP to the brink of their ultimate goal, and in doing so, clearly divided a nation. The Yes campaign often felt the need to emphasise that a Yes vote was not support for one man.

But where now?

Despite defeat the vote could have been cast as win for Salmond and the SNP. More powers have been promised by the other parties. And with a reported registration rate of over 97% the people of Scotland have engaged with politics and could be voting in numbers most western democracies have not seen in over a generation.

Salmond had said he would not resign as first minister should he lose. It seemed unlikely he would disappear from the Scottish political scene anytime soon. But one thing about Alex Salmond: he often does not do what is expected. And so it has proved again.

This article was updated on Friday September 19