“It's always difficult to avoid charges of being nostalgic if we talk about going back to things. Back to the past or forward to the past, but there are principles that existed in preindustrial/early industrial cities and which were overturned by key technological inventions of the late 19th and early 20th century, particularly the railway, the motorcar, of course, the internal combustion engine on which it’s based and which led to the vast expansion of towns and cities and, crucially, suburbanization where people who could afford it moved out of the more polluted densely populated inner areas into low density, better lifestyle-oriented suburbs and even beyond the suburbs into surrounding rural areas and were able to commute in by fast means to their workplace in the city, but the result of that is what we now face as the challenge of unsustainability. And as you rightly say, the key feature that still characterizes many European cities today–London, Paris, Berlin, many others, is the idea that they are composed ultimately of a series of–in London they like to call them villages–neighborhoods and areas that have multiple land uses and dense social networks of interaction within a small area. That principle, what is now called by Anne Hidalgo, the mayor of Paris, and being popularized more widely by the C40 Cities Climate Leadership Network and others as the 15 or 20 Minute City or 15 or 20 Minute Neighbourhood. The idea underpinning it is that a higher proportion of the goods and services, the activities, the social interactions that we need are obtainable within a 1 1/2 to 2 km radius of one's home, which means a far higher proportion of one's individual trips or multiple purpose journeys can be done on foot and by bicycle, therefore, you use your vehicle if you have one more sparingly. You use the bus or minibusses to reach slightly more distant places, and then you have transport interchanges is where you connect with the metro system or the best rapid transit or the railway to reach other parts of large cities or indeed for inner-city journeys. And that is what is now becoming the new best practice in terms of urban planning redesign both of existing urban areas to try to revitalize inner-city areas, other areas that are depressed and in need of economic regeneration and principles on the basis of which we need to design new areas, whether they are on the outskirts of bigger cities or in the context of middle and low-income countries designing entirely new cities which are going to be built over the coming 20 or 30 years and which, in terms of the number of people who live in them and the number of hectares or square kilometers that they will cover of the earth’s surface, will be equivalent to that built between the beginning of urbanization and the present day. It's a staggering thought, but if you think about it that way, it highlights the importance of new build, new design, according to our latest understanding of sound sustainability principles.”David Simon is Professor of Development Geography and Director for External Engagement in the School of Life Sciences and the Environment, Royal Holloway, University of London. He was also Director of Mistra Urban Futures, Gothenburg, Sweden from 2014–2019. A former Rhodes Scholar, he specialises in cities, climate change and sustainability, and the relationships between theory, policy and practice, on all of which he has published extensively. At Mistra Urban Futures, he led the pioneering methodological research on comparative transdisciplinary co-production. His extensive experience includes sub-Saharan Africa, South and Southeast Asia, the UK, Sweden and USA. From 2020-21, served as a Commissioner on the international Commission on Sustainable Agricultural Intensification (CoSAI), 2020-21. His most recent books as author, editor or co-editor are Rethinking Sustainable Cities: Accessible, green and fair (Policy Press, 2016), Urban Planet (Cambridge Univ Press, 2018), Holoca