David Miranda row: Seized files 'endanger agents'
30 August 2013 Last updated at 22:44 BST
Files seized from a Guardian journalist's partner contain details that could risk intelligence officers' lives, the High Court has been told.
Deputy national security adviser Oliver Robbins said one file seized from David Miranda included 58,000 "highly classified UK intelligence documents".
Mr Miranda, who denies this, was held for nine hours at Heathrow Airport under anti-terror laws on 18 August.
Tom Symonds reports.