John Prendergast is adamant that people power is the way to get politicians to act.

"We have to make them care, " says the Washington-based Prendergast. "We have international systems and response mechanisms, which can work when the political will is generated. The problem is because these crises often happen half-way around the world, politicians perceive no strategic interest in intervening. Then these conflicts and emergencies bleed on until people are so shocked they act, often when it's too late."

The situation in Darfur should be shocking enough. Over the past half-decade the Sudanese government has been supporting a campaign of rape, murder and pillage by the Janjaweed an Arab militia. Up to 400,000 people have been killed in Darfur since 2003 and thousands of women are being systematically raped. Prendergast calls it "Rwanda in slow motion" and he and his famous co-author are at pains to point out genocide has become a shameful fact of life.

There are many reasons why the international community is slow to intervene, from business links to petty political rivalries.

One key issue is the simplistic parameters of the War on Terror. "Bush had been very clear you were either with us or against us after 9/11, and the Sudanese government has decided it'd be with us. So they got a free pass, like every other dictatorship that has been supportive of Bush."

Much of Prendergast's work involves lobbying people from Bush's administration and other regimes which are equally culpable. He admits it can be difficult to keep his cool when trying to engage people he feels are partly responsible. "At first I was often inappropriate!" he says with a laugh. "I would escalate prematurely into accusations and moral indignation, which never works on politicians. Now I've learned moral indignation plus shouting doesn't really accomplish anything when you're dealing directly with politicians and policy-makers.

A level-headed empirical approach is much better. Well that's the learning curve I've been on for the last quarter century!"

The book traces some of this learning process, but it also contains the story of the friendship between Cheadle and Prendergast. Amidst their account of the Darfur tragedy is a story of two hip young guys shooting hoops. "We met at this screening for Hotel Rwanda at the Holocaust Museum, " says Prendergast. "We became friendly because we were both young American guys who were into sports. We jawed about basketball and I don't think we even mentioned Darfur the first couple of times we met. But when we were both invited on a congressional delegation there, we broke off from the congress people, and with our friend Paul Rusesabagina, who Don portrayed in Hotel Rwanda, we went off on our own mission to Rwanda, Eastern Chad, and across the border into Darfur. Five months later we went on another trip into northern Uganda and travelled around that conflict zone. Those two trips really solidified our partnership. We developed a real friendship in the midst of that human suffering."

It was clear to both they had a chemistry that could be used to spread the word about the horrors they had witnessed and they began campaigning. "We started doing TV and radio shows and op-eds and speeches. We had our shtick. We had our set routine. There were stories we could tell about the region, and I guess it was a natural evolution we would just put it all in one place."

And the book is their shtick to some degree. It contains occasional digressions about friends and family, and there are even lapses into buddy-movie style dialogue. It serves to humanise them, which is apt because Prendergast is adamant ordinary humans can make a difference. He is clearly in awe of the actions of the masses of regular men and women who agitate for change, and he takes pleasure in recounting how people from all walks of life are beginning to act on issues like Darfur. Prendergast thinks there's something in the air.

"I think it's a very exciting time. It isn't just about going to concerts, singing along and giving $100. That's important, but now it's also about people joining internet organisations and writing letters to parliamentarians and demanding action. People are connecting globally with other like-minded groups about issues like HIV, the anti-genocide effort and the peace movement. I think we have the beginnings of a strong lobby for social justice across the world."

He also feels everyone can have a role in this new movement and that, despite what the cynics say, includes celebrities like Don Cheadle. "I'm an unabashed supporter of the involvement of celebrities in issues like this.

Take African trade . . . we would have had about 36 people in the United States who cared about African debt issues if Bono hadn't led that campaign. Yesterday I met an aid worker who went to the Balkans because she read an essay by Angelina Jolie, and it changed her life. The celebrity activists get people in the door. Once they're in it's up to us activists to keep them there, but the celebrities are like recruiters on steroids.

They get criticised all the time, but anyone I've met has been very serious about the issues and has been a very beneficial ally."

Talking to Prendergast and reading his book is a strangely uplifting experience.

Despite the horrific events he describes, he still has a lot of hope. He thinks things can get better. In fact, he knows they can. "I went to Sierra Leone last week for the election, " he says.

"Five years ago they were in the middle of a war, a brutal war, now there's a democratic election, a positive economic growth rate, and the child soldiers are being reintegrated in society. The real story of Africa is about transformation and redemption, not commiseration and disaster, and frankly that makes it easier to continue."

He is also relentlessly positive about the international network of activists he has met and encourages us to join. In fact, he makes it sound like fun. "This not about a bunch of people sitting around depressed, glumly chanting 'woe is me and woe is Darfur'. Some of the most interesting people I've met in my whole life I met because of these issues. These people are extraordinary and the chance to meet them and work with them is really an honour. I get up every day and I don't know what's going to happen." he pauses. "It's really been a great life."