Vladimir Putin left last year’s G20 meeting in Brisbane early in a huff, tired of being chided by world leaders over Ukraine. Twelve months on, an audience with the Russian president was one of the hottest tickets in town, as western leaders were forced to recognise the road to peace in Syria inevitably runs through Moscow. Few at the annual summit of world leaders have seen such a transformation in their fortunes, or appeared to enjoy it as much, as Mr Putin moved from a scolded diplomatic outcast to a self-styled problem-solver the west cannot ignore. Whether it was shifting air strikes to target Isis rather than Syrian rebels, or backing a political settlement in Ukraine and offering a debt restructuring deal, Mr Putin felt he held all the cards as the west came to him for answers.