The fact that people are no longer tied to specific places for functions such as studying or learning, says Mr Mitchell, means that there is “a huge drop in demand for traditional, private, enclosed spaces” such as offices or classrooms, and simultaneously “a huge rise in demand for semi-public spaces that can be informally appropriated to ad-hoc workspaces”. This shift, he thinks, amounts to the biggest change in architecture in this century. In the 20th century architecture was about specialised structures—offices for working, cafeterias for eating, and so forth. This was necessary because workers needed to be near things such as landline phones, fax machines and filing cabinets, and because the economics of building materials favoured repetitive and simple structures, such as grid patterns for cubicles.