Decentralisation is not a new idea, particularly within government. Cycles of centralisation and decentralisation have been an integral part of human history: it is often argued that it was the decentralisation of the city states which led to the success of ancient Greece and that the political centralisation of ancient Rome contributed to its downfall. More recently, and closer to home, the UK has been grappling with decentralisation in the form of devolution and the introduction of elected ‘metro mayors’.

But what do we really mean by decentralisation? It describes the process of distributing power away from a central authority or location so that no single individual or group makes decisions on behalf of all the parties. Decentralisation or centralisation is not a binary option; rather they lie on a spectrum, with nearly all systems and organisations falling somewhere between being totally centralised and totally decentralised. So when something is described as being ‘decentralised’, this is often in comparison to what existed beforehand. While in this collection we use the terms ‘decentralised’ and ‘distributed’ interchangeably, some use ‘distributed’ only to refer to systems that are totally decentralised.