There is increasing interest among funding agencies to understand how they can best contribute to enhancing the socio-economic impact of research. Interdisciplinarity is often presented as a research mode that can facilitate impact but there exist a limited number of analytical studies that have attempted to examine whether or how interdisciplinarity can affect the societal relevance of research. We investigate fifteen Social Sciences research investments in the UK to examine how they have achieved impact. We analyse research drivers, cognitive distances, degree of integration, collaborative practices, stakeholder engagement and the type of impact generated. The analysis suggests that interdisciplinarity cannot be associated with a single type of impact mechanism. Also, interdisciplinarity is neither a sufficient nor a necessary condition for achieving societal relevance and impact. However, we

identify a specific modality -- "long-range" interdisciplinarity, which appears more likely to be associated with societal impact because of its focused problem-orientation and its strong interaction with stakeholders.