SCOTTISH independence was in Gordon Wilson’s DNA.

Back in what he described as the "dark days" of the 1980s, his colleague Jim Sillars said it was the former leader’s hard work and dedication that not only kept alive the SNP but the dream of independence too.

Yet there were times of late when Mr Wilson caused the current leadership some added turbulence over just when or when not to seek a fresh vote on Scotland’s future following the referendum defeat of 2014.

Born in Govan in 1938, the son of a butcher’s van driver graduated from Edinburgh University in the early 1960s and worked as a solicitor in Paisley.

Before he entered Parliament, he co-founded the political pirate radio station Radio Free Scotland and within the party held a number of posts, including that of National Secretary from 1964 to 1971.

In the 1970s, he was at the forefront of the Nationalists’ “It’s Scotland’s oil campaign,” having coined the slogan himself.

In 1973 Mr Wilson narrowly failed to win the Dundee East by-election but a year later at the General Election took the seat and was part of the successful SNP campaign in which 11 MPs were elected.

The Glaswegian-cum-Dundonian was the party’s deputy leader at Westminster during the years of Wilson/Callaghan governments from 1974 to 1979, serving as the SNP’s spokesman on oil and energy as well as on devolution.

In his book, “SNP: The Turbulent Years 1960–1990,” Mr Wilson admitted there were tensions between the party’s MPs in London and its officers in Scotland; particularly the formidable Margo MacDonald.

When in 1979 after the Nationalist contingent at Westminster fell from 11 to just two, he was elected national convener.

Then came those “dark days” of internal turmoil when he was at the forefront of condemning factions such as Siol nan Gaidheal, whom he branded “proto-fascist,” and and the 79 Group, which wanted to take the party to the Left and who included among its leading lights, Alex Salmond, who would later become party leader. The group was expelled from the party in 1982.

Mr Wilson led the Nationalists through two poor election performances and the high Conservative watermark of the 1980s; although one bright spot was the Glasgow Govan by-election of 1988 when Mr Sillars beat off the Labour challenge to become the local MP.

In the late 1980s, the SNP initially participated in the Scottish constitutional convention, which was set up to create a framework for Scottish devolution.

But Mr Wilson together with Mr Sillars decided to withdraw its participation because of the convention's unwillingness to discuss Scottish independence as a constitutional option.

In 1990, he was succeeded as party leader by Mr Salmond.

Eight years later, the former leader was selected as a candidate for Scotland in the 1999 European Parliament elections but came too low down the SNP's list to be elected.

In 2010, the former MP co-founded Solas, a Christian body dedicated to the revival of the faith.

In addition to writing several books about his time in the SNP, he rose to prominence again as an active campaigner for independence in the run-up to the Scottish referendum of 2014, setting up the think-tank Options for Scotland with Mr Sillars.

In recent times, Mr Wilson became one of the SNP's most prominent internal critics of an early referendum linked to Europe.

Earlier this year, he said another independence poll would be "at the worst possible time". The former leader accused the current SNP leadership of "unpreparedness" and "vacuum and drift".

A Eurosceptic, he criticised the SNP's "obsession" with Europe, which he said risked making a Yes vote synonymous with a "non-deliverable" return to EU membership.

He had argued that organising a new vote so soon after the previous one could be a miscalculation and that Scotland needed to be more prepared before it voted again.

But in March he performed a spectacular change of mind after the First Minister called for a second referendum because she had not got a bespoke deal for Scotland on Brexit.

Declaring his “full support” for Ms Sturgeon, Mr Wilson said: "Regardless of my personal views, the die is almost completely cast. The only way we can win is to throw our whole being into the fight for Scotland's liberty both body and soul.

"It is a clear case of 'who dares, wins'. Half measures will fail," he added.

Describing her colleague as a “passionate advocate for Scotland…a true patriot,” Ms Sturgeon in her tribute noted: “Gordon was always forthright in his views and his commitment to seeing Scotland become an independent country was second to none. Even - perhaps especially - on those occasions when his views on tactics differed from mine, I always highly valued and appreciated his advice.”