Participants of G20 summit started to arrive at St. Petersburg airport on Wednesday (September 4). Among the first guests who arrived in the morning were South African President Jacob Zuma and IMF Managing Director Christine Lagarde.

The Group of 20 cut its teeth in the global financial crisis of 2009, achieving unprecedented cooperation between developed and emerging nations to stave off economic collapse which has not been matched since.

Four years on, shifts of power and money - led by capital flight from emerging markets - and gaping divisions over Syria will test the resolve of the G20 leaders when they meet in Russia's second city of St Petersburg this week.

It is the very breadth of the forum, which groups developing and developed economies accounting for two-thirds of the world population and 90 percent of its output, that makes it hard to forge a united front.