This draft report from 12 February 2010, prepared by officials from the UK intelligence services for review by the Cabinet Office and HM Treasury is frank about the challenges brought about by bulk collection: see the Intercept article Facing Data Deluge, Secret U.K. Spying Report Warned of Intelligence Failure, 7 June 2016.
This concluding slide from an undated GCHQ presentation on Tempora reminds analysts that they are in a “enviable” and “privileged” position – “you have access to a lot of sensitive data… have fun and make the most of it”: see the Guardian article Mastering the internet: how GCHQ set out to spy on the world wide web, 21 June 2013.
These July 2009 documents provide a full list of the fibre-optic cables GCHQ had access to at that point, including details of location, bandwidth and corporate partners: see the Süddeutsche Zeitung article Snowden-Leaks: How Vodafone-Subsidiary Cable & Wireless Aided GCHQ’s Spying Efforts, 25 November 2014.
These screenshots from GCHQ’s internal GCWiki describe progress on the MTI (Mastering the Internet) cable access project, also known as Tempora. Prominent within these reports is the close cooperation with corporate partner Cable & Wireless / Vodafone, codenamed GEROTIC: see the Süddeutsche Zeitung article Snowden-Leaks: How Vodafone-Subsidiary Cable & Wireless Aided GCHQ’s Spying Efforts, 25 November 2011.