I have long been intrigued over the role of the public in the early identification of terrorist plots, with post scattered in several threads and hearing a variety of high-level speakers give differing answers, or no answer at all.

Hat tip to an Indian friend who pointed to a US study I'd missed:
research done by North Carolina based Homeland Security Solutions, a private group, proves this. They examined 86 terror attacks between 1999 and 2009. Of this, 18 were carried out, including 9/11; 68 were foiled; 20 each were detected by the public and federal agencies, 13 through advance intelligence and the local police detected 15.
The cited report awaits reading and I shall return another time, meantime the summary states:
More than 80% of foiled terrorist plots were discovered via observations from law enforcement or the general public
The link is:https://www.ihssnc.org/portals/0/Bui...lues_Strom.pdf

In the UK historically there has been very little public information, although of late officialdom cites two examples.

This is a thread in progress.