“The world is on an unsustainable path… We have to rethink how this all works… We have to change or we won’t exist in 20 to 30 years.”

This could have been the UN Secretary-General at the opening of the COP25 conference in Madrid. In fact it was Peter Mather, head of BP in the UK and Europe, at Aston University for a Tortoise ThinkIn.

The event was the first of three to focus on the question of whether we should stop using fossil fuels altogether. The consensus answer was yes – in principle. As Professor Hongming Xu put it, we’d stop using them tonight if it was possible. But what is possible in the real world, where 7.7 billion people and counting need energy to live and feed and clothe themselves?