For many of the leaders flying into London for tomorrow’s G20 summit, it is make or break time for world economic stability. But before any concrete measures can be adopted, the various nations have to address fundamental differences on the scale of economic stimulus plans and regulation of the financial sector.The British Prime Minister, whose country is the chair of the G20 this year, is desperately seeking consensus. Gordon Brown said: “What all these challenges have in common is that none of them can be addressed by one country or continent acting alone, none of them can be met and mastered without the world coming together and none of them can be solved without agreed global rules informed by shared global values.” France is one country threatening not to sign the final communiqué if progress is not made in key areas, especially on the question of reforming the global financial system. French President Nicolas Sarkozy said: “We have to get results. There’s no choice. The crisis is too serious to allow us to have a summit for nothing.” Many countries have already been holding pre-summit meetings and think-tanks, but key players are warning that one summit is not going to be enough. Observers say wrapping things up in London with a sense of unity on the way forward will be the biggest challenge.