This paper explores the debate about the pursuit of an integrated and participatory approach to sustainable development within the UK planning system, using the Examination in Public (EiP) of the Hertfordshire Structure Plan as a case‐study. The Hertfordshire Structure Plan incorporated a concept called ‘whole settlement strategies’, requiring that the major settlements in the county were planned holistically to assess their potential to meet development needs. The debate at the EiP sheds light on issues associated with the operationalism of key themes of sustainable development in planning, and on the relationship between emerging approaches to Local Agenda 21 and the development plan system. It also highlights the contested meanings of sustainable development between those promoting a strong approach and those holding to a weak definition based on meeting development needs.