"The September meeting of finance ministers was also the subject of a new technique to provide a live report on any telephone call made by delegates and to display all of the activity on a graphic which was projected on to the 15-sq-metre video wall of GCHQ's operations centre as well as on to the screens of 45 specialist analysts who were monitoring the delegates.

"For the first time, analysts had a live picture of who was talking to who that updated constantly and automatically," according to an internal review."