This page from GCHQ’s internal GCWiki, dated 27 May 2009 describes a system for querying mobile phone information acquired during port stops: see the Intercept article Airport Police Demanded An Activist’s Passwords. He Refused. Now He Faces Prison In The UK, 23 September 2017.
This GCHQ briefing from September 2009 describes the tools then available to analyse metadata collected on a massive scale: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.
This GCHQ presentation from 2011 provides the background to the agency’s hacking attack on Belgacom: see the Intercept article Operation Socialist: The Inside Story of How British Spies Hacked Belgium’s Largest Telco, 13 December 2014.