Standing on the doorstep of Tariq Ali's impressive Highgate house, the echo of the rung bell fading, it feels like an auspicious day to visit. Flicking through the paper on a stuttering train en route to leafy North London, there was a story about the first public sighting for four years of the 82-year-old Cuban revolutionary Fidel Castro.
Wearing a white, Nike tracksuit and looking spritely for an octogenarian, it transpires the pictures are a first volley in a media salvo mainly aimed at the US by the veteran revolutionary. Given that Ali, the Pakistani-born, London-based historian, novelist and firebrand commentator, has a long-standing antipathy to what he describes as American "imperialism", I assume the photographs will at the very least, amuse him.
As it turns out, Ali isn't that bothered.
"Well, actually, they're not the first photographs of him," he says sounding decidedly unimpressed. "Oliver Stone has interviewed him twice over the last three years. Oliver Stone has had amazing access to him and there are photographs of them together. Anyway, he seems alive and well." Ali shrugs his shoulders.
Ali has collaborated with the maverick American director on his new film, South of the Border. Already known for his fascination with presidents, Stone has previously made films about John F Kennedy, Richard Nixon and George W Bush, but South of the Border is something different. Ostensibly a documentary, it focuses on the rise of President Hugo Chvez of Venezuela and his reformist allies in South America, including Evo Morales of Bolivia. It's an unapologetically celebratory portrait. Shown first at the Venice Film Festival last year, and having already had its New York premiere, it's proved to be just as controversial as Stone's previous offerings, with critics objecting to both inaccuracies and its glowing assessment of Chvez.
"It's very simple, very straightforward," says Ali, sounding every bit like a man used to and happy about, ruffling feathers. "Its aim was very clear: in the United States in particular, but in Europe too, there has been so much disinformation about the South Americans and the Latin Americans, we just said let's hear them speak. You hear the other point of view non-stop so there was no attempt to make a balanced documentary in that sense."
Ali has written books about 9/11 (The Clash of Fundamentalism), the invasion of Iraq (Bush in Babylon), Pakistan's political situation (The Leopard and the Fox) and the rise of the reformist movement in South America (Pirates of the Caribbean: Axis of Hope). His involvement in Stone's film, which he ended up co-writing, came about by accident, though. Stone contacted Ali to interview him about America's role in world politics, and it was months later at a meeting in Los Angeles when he was asked to look over a rough-cut of South of the Border.
"To be perfectly frank, it was very messy," he says with trademark candour. "It was just, I thought, the wrong way to go about it." Ali, of course, told Stone this and Stone and producer Rob Wilson asked Ali if he would come on board to assist. He did.
"The strengths of the documentary really are Oliver Stone, a radical Hollywood producer, getting angry about media coverage of South America, hopping on a plane and, in two weeks, meeting seven presidents. That's quite astonishing. We took out every extraneous thing and made it into a political road movie."
It's a neat definition, allowing Ali to side-step the criticisms that have been levelled at the film, accusations that it is little more than agitprop, an uncritical, unbalanced celebration of leaders about whom questions have been raised in relation to suspected human rights abuses, less than subtle political bombast (Chvez famously called George W Bush "the devil" in one speech) or limits of free speech. Ali is unperturbed. For him, what is being achieved in South America is a "beacon" for the rest of the world. Any lack of balance in the film cannot begin to compete with what he sees as the wholesale character assassination of Chvez and his compatriots at the hands of the global media.
"The frightening thing about the power of the big media corporations today is that they present one view. We're not just talking about the tabloids, we're talking about the Financial Times, the Economist, the New York Times, the Washington Post, big mainstream serious papers and magazines.
"(The coverage] is hostile and the pattern is the same. That's frightening. Not one of these big papers thought: hang on a minute, surely just for the sake of diversity we should allow the other side to have a go."
Listening to Ali speak, it's difficult not to register how odd a voice like his sounds in our contemporary political culture. Openly ideological ("I believe that the capitalist system is a system designed to privilege the few, it doesn't even hide that, so it's not a system that can deliver") scathing of "back-room" politics and spin ("If you look at New Labour and the coalition what is there to choose between them? Really very little"), polemical, Ali's is a voice that jars in our political culture. That is precisely the reason, he says, that his events at book festivals and the lectures that he gives attract huge audiences. People want to engage in these debates.
What is fascinating about Ali is that, in large part, his views have hardly changed. In 1978 he wrote of "the key importance of the working class as the only agency of social change". Sitting in his beautiful drawing room, with glass doors that open on to a long, mature garden ("we were lucky when we bought it, completely unaffordable now" is how he bats away my compliments) when I ask him what it would take to change our political system his words are remarkably similar. "Mass action from below," he says without hesitation. "I honestly don't think that without that things can change."
He acknowledges that we're far from being able to achieve that, but he does believe that we can learn from what's going on in South America.
"People all over the world were told there is absolutely no alternative, you just have to accept what capitalism is dishing out. There is an opinion poll survey in the Financial Times that shows that 60 to 70 per cent of Europeans are in favour of cuts as the only way out of this crisis. That is astonishing. It shows a defeated population."
Ali would much prefer the South American model where, in the face of severe economic hardships, the response has been completely different. "They've been fighting privatisation, they've been resisting. And these are people who were in many cases non-educated people, semi-literate people fighting, knowing privatisation was wrong. Bolivian peasants, Peruvian peasants, they've shown far more guts in defending their rights than European workers and trades unions who caved in and collaborated, essentially."
Born in 1943 in Lahore in what was then British India and which became four years later, Pakistan, Ali's parents were communists. Politically aware and engaged even in his teens, he was sent to Oxford University in 1963. Nearly 50 years later, there remains an echo of a student firebrand, the young man who became the president of the student union, who demonstrated against Vietnam, who idolised Che Guevara. A true citizen of the world, he first travelled to South America in 1967. He's been going back ever since. But isn't he nervous about the personality cult which surrounds the new breed of South American leaders?
"Contact between politicians and the people here is essentially through the media. Evo Morales in Bolivia is seen by 80 per cent of Bolivians as their Nelson Mandela, the first indigenous president elected. When I was in Bolivia in the little shopping markets they were trying to sell me a poncho. I said 'no thanks, it doesn't suit me' and they said 'Evo wears it'. There's a real sense of pride now they've got one of their own in power.
"The policies that they are adopting are all essentially leftist social democratic policies which were considered normal in Europe after the Second World War. Using the state to run things, giving the poor a chance. I call it bailing out the poor, that's what these governments have been doing to one degree or another."
Although he thinks we can learn from South America that a different kind of system is possible and that democracy really can work, when it comes to our politics, Ali is as harsh as he is pessimistic.
"The culture here is such that if there's a problem you're encouraged to see it as the fault of an individual not the system. So when the economic system collapsed the media played it big on look at these fat-cat bankers earning however many millions a year. That's true, that's obscene, but the question is how come they are able to do that? No regulations, politicians approved it all. You have demonstrations outside the private home of the guy who ran the Royal Bank of Scotland (Sir Fred Goodwin] a disgusting figure in my opinion, but that's not the problem, it's a safety valve."
I wonder how, having been a voice of opposition for more than 40 years, Ali can be bothered? His prognosis is grim and yet to keep on talking, to keep on writing the books and trying to change the terms of the debate, at some level he must feel optimistic? "I guess I must," he says sounding utterly unconvincing. With his laptop lying on the table between us he tells me he is generally positive about the power of the internet. What he finds wonderful is the ability to mobilise people very quickly. A situation occurs - an aid flotilla destined for Palestine being stopped by Israel's armed forces is his example -- an e-mail is sent out, a demonstration takes place.
"I sometimes think if we'd had that in the 1960s we might've made a revolution." He laughs.
South of the Border opens on selected release on Friday. Tariq Ali appears at the Edinburgh International Book Festival at 4.30pm on 25 August, www.edbookfest.co.uk
• This article first appeared in The Scotsman on 25/06/2010