Ultimately it boiled down to an Obama-brokered handshake between Hu Jintao and Nicolas Sarkozy, according to US officials. The reality may be more prosaic, and the agreement of a final summit text on Thursday was the culmination of weeks of work by officials from 20 countries. But Barack Obama's self-effacing approach to summitry – one that was on Thursday remarked upon by several non-US officials – certainly did no harm.

According to senior US officials, towards the end of the summit Mr Obama pulled Mr Sarkozy and Mr Hu aside in full view of the plenary session with several officials and translators in tow.

The US president then brokered a compromise between his Chinese and French counterparts on an issue so arcane and inconsequential that it is hard to believe failure to have done so would have led to a collapse of the summit.