An interesting Real-Time Club dinner last night, featuring a speech by ex-MI6 Chief Sir Richard Dearlove and an hour of discussion. One of my favourite comments of the evening (Chatham House rules forbid me from attributing!) was that "intelligence is banal" — it is about piecing together many pieces of mundane information to create something useful.
There was also much debate about the effectiveness of the UK's intelligence agencies. One attendee pointed out major successes in halting Libya's progress towards nuclear status and in forcing the IRA to the negotiating table. I would recommend UK Eyes Alpha by Mark Urban for a counterpoint. Urban's conclusion in 1997 was that UK agencies had failed to provide value for money since the end of the Second World War, funking the Cold War and other tasks. The Irish War by Tony Geraghty has excellent coverage of the activities of intelligence agencies and special forces in Northern Ireland.
Another interesting comment was that while compartmentalisation during the Cold War kept HUMINT and SIGINT separate, they are now much better integrated. Critical to the agencies' work is analysis of vast quantities of data obtained from communications providers, banks, airlines and other industry sectors. In other words, even if you are paranoid, they are still out to get you :)