Report of the Bulk Powers Review (PDF) by David Anderson Q.C. Independent Reviewer of Terrorism Legislation. (Web version)
From its webpage:
This report includes the findings of the independent review of the operational case for bulk powers, which will inform scrutiny of the Investigatory Powers Bill.
If you find yourself dissatisfied with the sound bite and excerpt commentaries on this report, you may find the two hundred and three (203) full version more to your likely. At least in terms of completeness.
I have glanced at the conclusions but will refrain from commenting until reading the report in full. It is possible that Anderson will persuade me to change my initial impressions, although I concede that is highly unlikely.