T he Excel centre, a windswept complex deep in London's Docklands, is best known as the venue for an annual boat show. On Thursday it is instead the destination for a flotilla of limousines as US president Barack Obama and other leaders assemble in an effort to rescue a shipwrecked world economy.

Central to the Group of 20 summit of industrialised and developing countries will be the question of whether the chaotic system of finance that swept the globe over the past two decades can be controlled. It is the equivalent of installing seatbelts, airbags and anti-lock brakes on cars that have just been involved in a head-on collision. If they succeed, driving should become safer. But some motorists may forsake the highway for slower country lanes.