Why do development projects so often fail to deliver progress, yet succeed in strengthening states? Central Margins answers this question by exposing the paradox at the heart of development: economic failure masking political success. Through vivid ethnography and deep archival research, the book shows how Sri Lanka's ambitious programmes – most notably the World Bank–funded Mahaweli Development Scheme – collapsed as projects of prosperity but triumphed as tools of militarisation, demographic engineering, and state consolidation. Introducing the concept of 'hidden state transcripts', it reveals how governments project images of benevolent development while embedding surveillance, displacement, and majoritarian nationalism in everyday life. By analysing state power from the contested margins of the Sinhala-Buddhist state, Central Margins demonstrates how postcolonial regimes weaponise development and environmental governance to remake sovereignty. This original account speaks not only to scholars of South Asia, but to anyone interested in how development reshapes power and politics across the Global South.This title is Open Access.