The most successful piece of furniture ever made

Cast your mind back to 2020. Lockdown had shoved everyone in front of a webcam, and we all became unwitting voyeurs of each other's rooms – millionaire actors chatting to Graham Norton, politicians broadcasting from spare bedrooms, theatre companies stitching together productions over Zoom, journalists interviewing strangers. Once you started noticing, the same bookcase kept appearing in the background. Whoever they were, wherever they lived, the same plain, blocky, slightly-overstuffed shelves often stood quietly behind them. It was the IKEA Billy. And you probably own one. There aren't many objects that belong in both a broke student's room and a French château, but the Billy bookcase manages both with ease. Aggressively ordinary and quietly ubiquitous, it has become an icon of simplicity and distribution. Created in 1979, IKEA has sold more than 140 million of them – one rolls off the line every three seconds. Bloomberg has even used it as an economic indicator, comparing Billy's…