Throughout the first half of the 20th century, the working week gradually got shorter and shorter. As technological advances powered economic growth, workers reaped the gains not just in the form of higher pay, but more leisure time. The economist John Maynard Keynes predicted we'd eventually all be working a 15-hour week. Even in the 1970s the expectation that 8 hour days would be reduced to 6 was widely held across the political spectrum. But this all ground to a halt in the 1980s. In this edition of Analysis Sonia Sodha explores the great leisure mystery: whatever happened to this dream of working less? And why is the idea of a 4-day working week gaining traction on the political left in Britain? What would a society that ditches the long-hours culture, and re-embraces the leisure dream look like, and is it really possible to achieve this without increasing inequality between the haves and have-nots of the labour market?