This paper explores the inter-organisational collaboration between public and private organisations, i.e., the public-private partnerships (PPPs). The private sector is directly intervening worldwide in the delivery of public services and infrastructures. PPP is explored from the perspective of both sectors to gain insights that contribute to further understand of its meaning, implications, and functioning. The paper also aims at critically analyse the theory and practice relationship. Acknowledging that the British experience constitutes an international reference as far as PPPs are concerned, this paper focuses on the British National Health Service. With the aim of uncovering the dynamics and processes that involve that particular form of collaboration, multiple case study research was designed based on semi-structured interviews, focus groups and documentary data. Evidence highlighted the dependence on the socio-relational dimension for the development and characterisation of PPPs and that they are mostly driven by institutionalised forces. It was also confirmed that a transactional nature considerably improves the premises that accompany the rhetoric of partnership.