Blockchains, or ‘distributed ledgers’, are part of a new area of technology that is generating a lot of interest. They have the potential to become an important component of our global data infrastructure. In this report, we present an overview of Blockchain technology and issues that come with it, for a non-technical audience who seek to understand the potential of distributed ledgers and blockchains in a commercial or policy context. We focus on non-financial use cases, both to avoid duplication of other work and to explore the wider impact of the technology. Some of the key areas covered in this report are: Ÿ the basics of blockchain and distributed ledger technology Ÿ the landscape of use cases and applications Ÿ how blockchains will need to link into our global data infrastructure Ÿ how blockchains will need to grow and scale over time Ÿ the potential privacy implications for personal data in distributed ledgers, and the risk of adding personal information to blockchain systems without careful design Ÿ a practical exploration of building a blockchain system for data storage We conclude that distributed ledgers are a potentially important area of technology, but that we must avoid being swept up by ‘blockchain hype’, and remember to focus on solid user needs first, before we choose the technology that we will use. We recommend further that this is best done by organisations convening across sectors to identify common data infrastructure needs.