For his part, Mr Brown has written to the head of the civil service, Sir Gus O'Donnell to say "no minister and no political adviser other than the personinvolved" had knowledge of Mr McBride's emails.
Depending on who's getting arrested, and for what, warrantless searches of cell phone data could have wide-ranging potential to implicate not just the arrested person, but also to draw police attention to other people who might be involved (or merely associated) with the arrestee.