In a blunt admission after two days of preliminary talks at the G20 meeting of world leaders, the prime minister conceded little progress had been made – and the conference is not on track to achieve a deal that keeps the goal alive. He put the chances of success as “six out of 10”.

“Currently, let’s be in no doubt, we are not going to hit it and we have to be honest with ourselves,” he said. The commitments being made so far were a “drop in the rapidly warming ocean”.