Nowadays, grid and peer-to-peer (p2p) technologies have become popular solutions for largescale resource sharing and system integration. For escience workflow systems, grid is a convenient way of constructing new services by composing existing services, while p2p is an effective approach to eliminate the performance bottlenecks and enhance the scalability of the systems. However, existing workflow systems focus either on p2p or grid environments and therefore cannot take advantage of both technologies. It is desirable to incorporate the two technologies in workflow systems. SwinDeW-G (Swinburne Decentralised Workflow for Grid) is a novel hybrid decentralised workflow management system facilitating both grid and p2p technologies. It is derived from the former p2p based SwinDeW system but redeveloped as grid services with communications between peers conducted in a p2p fashion. This paper describes the system design and functions of the runtime environment of SwinDeW-G. Index Terms: Grid Workflows, Peer-to-Peer Workflows, E-Science, Coordination, Decentralisation