Process flexibility has been investigated in depth in the context of intra-organisational processes, but it is still an open issue when processes cross the boundaries of companies. In this paper, we address the modelling of flexible inter-organisational processes using a version-based approach. Indeed, versions are known to be a powerful technique to deal with variability, evolution and adaptation of processes, which are the three main needs of process flexibility. More precisely, this paper presents VP2M (Version of Process Meta-Model), a meta-model supporting the modelling of versions of inter-organisational processes, addressing both static and dynamic aspects of VP2M. It also illustrates process version modelling within the Subsea Pipeline process example.