Plastic bags have only been in common use for about 30 years, but they have become ubiquitous – UK shoppers use around 8bn bags every year, resulting in 100,000 tonnes of carrier bag waste, the same weight as 70,000 cars, according to Wrap, the government waste prevention programme.

But their days may be numbered. San Francisco passed a law in March banning plastic bags in the city’s supermarkets and pharmacies.