Original: The Chelseaâ "Hackney line (also referred to as the Chelney line, Kings line and Crossrail 2) is a safeguarded route for an underground railway running from south-west London (UK) to north-east London.
Simplified: The Chelsea-Hackney (or "Chelney") line is a safeguarded route for an underground railway running from south-west London to north-east London.