Lawyers acting for David Miranda win an order to stop the government and police examining data seized from him – except “for the purpose of protecting national security”.
David Miranda’s legal team were granted the order, which will run until Friday, 30 August.
The High Court will then consider further Mr Miranda’s application for an interim injunction to stop examination “until the legality of that seizure has been determined by this court”.
Matthew Ryder QC, appearing for Mr Miranda, told the court the legal challenge had been brought “to protect the confidentiality of sensitive journalistic material”.
Channel 4 News Home Affairs Correspondent Simon Israel, who attended the high court hearing, tweeted: “Met police tells court a criminal investigation has been launched after finding highly sensitive and greatly injurious material.”
In a separate tweet, he wrote: “no details of investigation. Lawyer tells court police are still going through tens of thousands of pages of material.”
Mr Miranda has launched an application for judicial review, arguing that his detention was a misuse of Schedule 7 of the Terrorism Act 2000 and breached his human rights.
The Brazilian is the partner of Guardian journalist Glenn Greenwald who has worked with US whistleblower Edward Snowden on a series of security services exposes.
Mr Miranda was held without charge at Heathrow Airport for the maximum time permitted under the anti-terror legislation as he changed planes on a journey from Berlin to his home in Brazil on Sunday.
#miranda: home office lawyer says seized material contains tens of thousands of highly classified documents which risks national security
— simon israel (@simonisrael) August 22, 2013
#miranda; met police tells court a criminal investigation has been launched after finding highly sensitive and greatly injurious material
— simon israel (@simonisrael) August 22, 2013
Thursday’s order was granted by Lord Justice Beatson and Mr Justice Kenneth Parker after hearing the home secretary considered it was in the interests of national security to examine the data “without delay”.
Outside court, solicitor Gwendolen Morgan, of law firm Bindmans, which is representing Mr Miranda, said the government now has seven days to “prove there is a genuine threat to national security”.
Asked what she knew about the news that there was now a criminal investigation, she said: “Very little. We don’t know of any basis for that.”