GCHQ works in partnership with the Security Service and the Secret Intelligence Service to protect the UK's national security interests GCHQ is one of the three UK Intelligence Agencies and a part of the UK's National Intelligence Machinery CESG is the Information Assurance arm of GCHQ and is the Government's National Technical Authority for IA responsible for enabling secure and trusted knowledge sharing, which helps its customers achieve their aims The Intelligence Services Act 1994 and the Regulation of Investigatory Powers Act 2000 underpin activities at GCHQ GCHQ's headquarters are in Cheltenham