My work at UCL explores the extent to which core concepts and principles from systems thinking and complexity economics could inform a richer understanding of sustainability issues applied to the built environment and how it can better leverage transformational change in this respect. Several fundamental properties are investigated in this respect, such as holism and interconnectedness; system boundaries and structures; open systems and non-linear dynamics; heterogeneity and sub-optimality; uncertainty and endogenous innovation; feedback loops, system constraints and time delays; and self-organisation, emergent behaviour and regime change. These core concepts could act as guiding principles or criteria when developing and deploying a range of quantitative and qualitative methods and models to investigate sustainability changes of the built environment. A further broad interdisciplinary topic that I have been tackling during my work at UCL is that of investigating the meaning of model validation and to what extent the criteria deployed for validation scientific models exploring sustainability issues and aiming to inform decision-makers need to be revised or expanded. Other research interests include: climate change economics and just transitions, the SDGs and city transformations, and the science-arts interface in relation to delivering low-carbon, socially-inclusive transformations. Network interactions, workshop organisation and discussions with UCL colleagues and beyond are an integral part of my work.