Plastic bags may be handy for carrying stuff around, but campaigners say they’re really bad for the environment. One of the UK’s supermarkets is going to start charging customers for plastic bags in the latest effort to try to cut the number used. Around 13 billion plastic bags are given free to UK shoppers every year. Each one takes 1,000 years to decay. Marks & Spencer is going to charge food customers five pence for every bag — with the profits going to green charities. It tried out the idea in some of its shops, and saw a 70 per cent drop in the number of bags handed out. The more bags we use, the more room we need to find to throw out all the old ones.