When talking about resource efficiency, SustainAbility, the think-tank and consultancy, cites some compelling company statistics: between 2005 and 2008, Wal-Mart cut its fuel consumption by 25 per cent – and the US retailer reckons an initial 15 per cent improvement in fuel efficiency generated savings of more than $40m a year.

Between 2002 and 2005, a programme to cut power wastage and use more renewable energy saved Pfizer, the pharmaceuticals company, $30m a year.