Today in Glasgow, the definitive biography of trade unionist, journalist, author and lifelong political activist Jimmy Reid was launched. Authored by Professor Alan McKinlay and Dr Bill Knox it has been written with the full cooperation of the Reid family.

As befits someone who was schooled in the post war politics of the Communist Party of Great Britain, Jimmy Reid could crunch any analysis through a rich seam of historical knowledge. Observations, compulsorily delivered with panache and accompanied by a lengthy rhetorical flourish, were not just about the here and now but were invariably put into a wider context.

This trait was in evidence when I was sitting in his house in Newark Drive, Pollokshields, a few years after Labour's 1997 election landslide. I was about to interview him about the then- Chancellor of the Exchequer, Gordon Brown.

Way back in 1983, when Brown was adopted as the candidate for the safe seat of Dunfermline East, Reid was a speaker at his adoption meeting along with the legendary National Union of Mineworkers figure, Lawrence Daly. Brown, ever shrewd and ever sensitive to the politics that would play with his constituency party, had chosen two speakers guaranteed to press all the right buttons.

Back to the interview about Brown. Although this was the early days of New Labour in government, Reid smelled an ideological rat. He paused, leaned forward and delivered his judgement of the Chancellor. "He is a tragedy and in my opinion could be the biggest traitor to the Labour movement since Ramsay McDonald." It was a soundbite and a half, even if in my estimation his case against Brown had been weakened by gross overstatement and an absurd historical parallel.

Jimmy Reid was a throwback to a Scotland that is the stuff of grainy film, to an era of heavy industry and ultra-strong unions of class politics and indeed class war of a time when the Labour party ruled supreme. His life charted some momentous events and, although the essence of his politics never really changed, the parties he voted for certainly did.

The Upper Clyde Shipbuilders crisis of 1971 was the momentous event that made him a household name. Forever immortalised by that famous speech in support of his comrades' work-in, he told them there would be "no hooliganism, no vandalism, no bevvying, for the eyes of the world are on us".

UCS was about the right to work, a mass movement that warned of ravaged communities if large-scale manufacturing was allowed to die. It was also one of those occasions when solidarity with the workers extended well beyond the shipyard gates. The shop stewards gave ownership of their struggles to all who had their labour to sell. UCS was a cry to save Scotland's industrial soul and in Reid, the cause had a man of effortless articulacy.

If he was the face of UCS, other Communists like Jimmy Airlie and Sammy Barr helped shape the strategy and it is a pity they are not as well known for their contributions which were every bit as great, something that Jimmy Reid would always acknowledge.

His voice had a sonorous quality, his delivery would quicken, driven by raw emotion but emotion guided by deep convictions. There was theatricality in his performance which was never faux. He was simply part of that generation who knew that the power of argument, emotively delivered, was a powerful tool in a trade unionist's armoury in deploying a case on behalf of members. He was a reminder that you don't need notes or a pre-written script to make a case if it is in your bones as well as your head and heart.

I remember that famous confrontation on Parkinson where he demolished an aggressive rant by the Carry On star, Kenneth Williams. Unfazed and unflappable, Reid simply bided his time before dissecting what he saw as nonsense from the angst-ridden comic actor. As a boy I remember being amazed that someone who spoke with my accent had triumphed on national television at a time when posh seemed to equal intelligent.

The essence of the Communist Party in industrial struggle was to maximise unity and solidarity and relegate tribalism and sectarianism lest it weaken a case and prove counter-productive. The guiding spirit of UCS in a sense summed up his politics.

During the miners' strike of 1984, he dismayed many by launching an attack on what he saw as Arthur Scargill's kamikaze strategy of not holding a ballot before strike action. The decision prompted disunity, split the Labour Party and engineered bitterness among people with essentially the same interests at heart. In a sense he saw the conduct of the dispute as the polar opposite of the unity-first principles that had guided UCS.

He moved from the Communist Party to Labour where he unsuccessfully contested Dundee East in 1979, losing to the about-to-be SNP leader Gordon Wilson.

Any notion of an elected political career was put on hold as he moved into journalism and broadcasting. He worked for both BBC and STV where he struck up a lifelong friendship with David Scott, who also worked for both broadcasters after a prominent career in newspapers.

From Labour he would commend the Scottish Socialist Party to people before settling on support for the SNP and independence. In this journey he was helped by the late John McFarlane, a Nationalist who, like Reid, had a fondness for Robert Burns.

I would bump into him sometimes in the Clutha bar or a Glasgow Southside hostelry or at soirees hosted by his friend, the former Labour Party chairman Bob Thomson. He was always generous with his time and keen to get my take on what was going on.

He loved debate, not argument rooted in a closed mind, but debate. He carried himself with the enthusiasm of a young man discovering politics for the first time and he could still engross himself in minutiae to make a point.

His was an authentic voice and at a key point in Scotland's story a necessary and impressive one. Unity of strength to deliver a unity of purpose in the goal of greater social justice was at the heart of what he believed in and he believed it whether in the Communist Party of Great Britain, the Labour Party or the SNP.

His contribution tells us that free spirits inevitably find the straightjacket of conformity that membership of a political party imposes is incompatible with being a prisoner of one's own conscience. His epitaph should be his values, not the parties he embraced. For him, these were mere transient vehicles for reform.