The introduction of a statutory right of access to open country and registered common land in England and Wales in 2005 was a major milestone in a campaign traceable to the 19th century, with views strongly polarized between social classes and political parties, and between land owners and campaigners. More recently, access has also been recognized as a factor contributing to quality-of-life, public health, social diversity and rural economic issues. The mapping of access land revealed that 55% of it is also designated Site of Special Scientific Interest, where wildlife is legally conserved. This has generated a need to assess the implications of access in each case, and take measures to ensure nationally and internationally important features are protected, drawing on sound scientific principles. Early research, although competently undertaken, often failed to address population-scale effects significant at the designated-site level, enabling disputes and polarized ‘beliefs’ to be articulated. Hence, in addition to drawing up formal and transparent procedures for evaluating impacts and resolving difficulties, funds were released and a major programme initiated, commissioning applied research of direct relevance to the implementation of the legislation. This has pushed forward the boundaries of knowledge in a field which is both difficult and expensive to study. By gradually replacing ‘belief’ with evidence, this represents a case study in resolving environmental disputes.