A secret report warned that British spies may have put lives at risk because their surveillance systems were sweeping up more data than could be analyzed, leading them to miss clues to possible security threats. […]
MI5 “can currently collect (whether itself or through partners …) significantly more than it is able to exploit fully,” the report warned. “This creates a real risk of ‘intelligence failure’ i.e. from the Service being unable to access potentially life-saving intelligence from data that it has already collected.” […]
The new revelations raise questions about whether problems sifting through the troves of data collected by British spies may have been a factor in the failure to prevent the Rigby killing. But they are also of broader relevance to an ongoing debate in the U.K. about surveillance. In recent months, the British government has been trying to pass a new law, the Investigatory Powers Bill, which would grant MI5 and other agencies access to more data. […]
https://theintercept.com/2016/06/07/mi5-gchq-digint-surveillance-data-deluge/