Britain’s leading supermarkets have pledged to drive down food and drink waste by a fifth within the next decade. Retailers including Asda, Sainsbury’s, Tesco and Morrisons are backing a voluntary agreement, which also targets a 20% reduction in greenhouse gas emissions created by the food and drink industry. Some 24 local authorities, including the London Water and Recycling Board, and major brands and manufacturers such as Coca-Cola, Nestle and Pizza Hut have also committed to…