The novelty is wearing thin. The eager anticipation and diplomatic hoopla that attended the London summit has given way to a certain weariness ahead of this month’s gathering of the Group of 20 leading nations. Back in the spring, leaders of the biggest economies could claim to have saved the world. What on earth do they do for an encore?

The G20 has outgrown itself. If you add in the myriad international and regional organisations, some 30 leaders will converge on Pittsburgh. The numbers could rise further. Some of those left off the guest list have gone to extraordinary lengths in the effort to gatecrash.