It has been nearly four years since Paul Martin stepped down as Prime Minister of Canada, but he still has a bit of the politician’s knack for schmoozing. He shook every hand, stood for every photo, and seemed to relish interaction with his audience at the Cambridge Union on Sunday.

In the slumberous world of Canadian politics, Martin is known as the man who spear-headed a remarkable decade of deficit reduction and surplus budgets as the country’s Finance Minister when his Liberal Party swept to power in 1993. He followed this up with a stint as Prime Minister, from 2003 to 2006, an underwhelming tenure that was largely overshadowed by party scandals, though it did produce some notable accomplishments, including increased spending on health care and the legalization of same-sex marriage.

Since then, Martin has morphed into something of an international statesman, equal parts activist and wise prophet who has been travelling the globe dispensing cautious warnings. And the role suits him. As Finance Minister, he was the chief architect of the G-20, the group of Finance Ministers and Central Bank Governors from 20 major economies that expanded the existing G-8 grouping. It is an accomplishment of which he is still, rightfully, very proud.

“The G-20 is the world’s steering committee,” he says. “We created it in the late 1990s, when it no longer made sense to not have countries like China and India at the negotiating table.” In the aftermath of the Asian financial crisis of 1997, Martin was among the first to recognize the need for a new grouping to deal with international economic crises. He worked tirelessly for it, and travelled around the world to lobby leaders and finance ministers personally. The work seems to have paid off. The call to bring Asian and Latin American powers into the fold seems prescient now, especially in light of the global recession that has demanded more co-ordinated action. At the most recent summit, leaders announced that the G-20 would be replacing the G-8 as the premier forum for the major economies of the world.

Martin spoke passionately about the need to act in Africa, referring to the continent as the “great opportunity of the 21st century.” According to him, “By 2050, two billion people will be living in Africa, including the youngest population in the world. That could be the next engine of global growth.” He chastised the G-20 for having ignored Africa so  far, and urged them to take responsibility.

Martin equally believes that G-20 has a major role to play in creating new financial regulation and taking action against climate change. He explained that regulation had to be co-ordinated between the major economies. “If you only have strong regulation in one place, companies will simply move to where the regulation is weakest.”

Responding to growing indifference to global conference-politics, Martin argues, “You can’t blame the G-20 for the failures of Copenhagen. The biggest problem in Copenhagen was too many people, and not enough hard discussion. That is exactly what the G-20 aims to overcome,” he explains.

Even at 71 he is firmly involved in countless campaigns. At times, he can even sound genuinely revolutionary. “We need to recast the idea of sovereignty by thinking of duties as well as rights,” he declares.

Yet, at the same time, Martin has a remarkable ability to couch his arguments in realistic, hard-headed pragmatism. He can speak to sceptics and win them over in their own language. “I am not asking for altruism, here. I’m not saying ‘Love thy neighbour’,” he says, “I’m just saying that it’s not possible to isolate yourself any more.”