Readers may recall the political fallout from a NYT story on the Manchester Arena bombing in May 2017, with Anglo-US law enforcement exchanging of information being turned off by the UK.
Link to NYT story, which now be behind a pay wall:https://www.nytimes.com/interactive/...s-photos.html?

Last week a US DoJ IG report found four employees mishandled sensitive information and two forwarded the email to their own personal email accounts. It gets worse, so read the linked story. The amazing fact the IG reported was that:
found misconduct by four of the more than 1,000 bureau employees who received an email containing the intelligence. (At the end) The inquiry found that British authorities had sent the report to “numerous other” US agencies, suggesting the leak may not have come from the FBI.
Link:https://www.theguardian.com/us-news/...g-report-finds

It is well known that the Anglo-US CT LE relationship is very close, but one does wonder if the "need to know" principle is being applied.