Every week, more than one hundred million Americans shop at Wal-Mart (93 per cent of the population every year), and 138 million visit its stores worldwide each week. Since their takeover of Asda, they have become, worryingly, the second largest retailer over here. Not bad going for a business that started life as a small bargain store in a remote corner of Arkansas in 1962.

This powerful, privately controlled institution inevitably lays itself open to criticism, partly because of its sheer size and power – which affects suppliers, customers and employees alike – but also because of its Victorian attitude towards unions, the low wages it pays its workers, the exploitation of overseas sweatshops, and