CHAIN is a multi-agency database recording information about people sleeping rough and the wider street population in London. The system, which is commissioned and funded by the Mayor of London was formerly managed by St Mungo's, now run by HomelessLink, represents the UK's most detailed and comprehensive source of information about rough sleeping.
CHAIN allows users to share information about work done with rough sleepers and about their needs, ensuring that they receive the most appropriate support and that efforts are not duplicated. Reports from the system are used at an operational level by commissioning bodies to monitor the effectiveness of their services, and at a more strategic level by policy makers to gather intelligence about trends within the rough sleeping population and to identify emerging needs.