Lawyers for David Miranda, the partner of Guardian journalist Glenn Greenwald, appeared in the High Court in London on Thursday, seeking an injunction to stop access to the material seized from him by British police.

Miranda, a Brazilian national was illegally detained at Heathrow Airport on Sunday and questioned for nine hours. Under the draconian provisions of Section 7 of the UK Terrorism Act 2000, he was denied the right to a lawyer and to remain silent. Nine of his personal items were seized, including his computer, cell phone, camera, and memory sticks.

The memory sticks are alleged to contain material pertaining to information leaked by former US National Security Agency contractor Edward Snowden on the mass surveillance techniques employed by US and UK spy agencies. Greenwald has collaborated closely with Snowden, who has been forced into exile in Russia in the face of US efforts to railroad him on charges of espionage.

After hearing submissions from Miranda’s legal representative and those representing the Metropolitan Police (Met) and the UK’s Home Office, judges Lord Justice Beatson and Justice Kenneth Parker granted a limited injunction supposedly preventing the government and police from “inspecting, copying or sharing” the data seized. This, however, was effectively ruled null and void by their judgement that police could examine the data for “national security purposes.”

A full hearing on the issue is to take place on August 30.

In another blatant denial of Miranda’s democratic rights, the Guardian reported that the ruling also allows authorities to investigate whether the 28-year old is “himself involved in the commission, preparation or instigation of acts of terrorism.”

Miranda’s solicitors had given the Met until Tuesday afternoon to state there would be “no inspection, copying, disclosure, transfer, distribution or interference, in any way with our client's data”. The deadline expired with no action.

In a letter to Home Secretary Theresa May and the Met, Bindmans, the London firm representing Miranda, stated that their client’s detention “amounted to a frustration of the legislative policy and objects of the Terrorism Act 2000” and was for “an improper purpose and was therefore unlawful.”

“The decisions to use schedule 7 powers in our client’s case amounted to a grave and manifestly disproportionate interference with the claimant’s rights” under European human rights legislation, it noted.

Bindmans initiated legal proceedings to “protect the confidentiality of the sensitive journalistic material.”

“If interim relief is not granted then the claimant is likely to suffer irremediable prejudice, as are the other journalistic sources whose confidential information is contained in the material seized by the defendants”, they warned.

In court, Matthew Ryder QC, representing Miranda, asked for a 14-day freeze on the inspection of Miranda’s phone and computer. He also requested that the police reveal with whom they may have shared information they had taken. Ryder said Miranda’s possessions were seized “under threat of criminal prosecution in a coercive use of Schedule 7 which was unlawful.”

Jonathan Laidlaw QC, representing the Met, said that the counterterrorism unit, SO15, had opened a criminal investigation, adding, “I am not prepared to alert defendants here or abroad about the criminal investigation that has begun.”

Laidlaw said the data seized contained “highly sensitive material the disclosure of which would be gravely injurious to public safety”. Preventing police from continuing their inspection “would be [a] dreadful situation to confront the police [with], bearing in mind the results of the part of the assessment it has been possible thus far to undertake.”

Steven Kovats QC, for the Home Office, also claimed “Material taken from the claimant includes material the unauthorised disclosure of which would endanger national security of the UK and put lives at risk.”

The Home Office argued in court that a ruling on the legality of Miranda’s detention and the seizure of his documents would be completed months from now or longer, if it was required to be made in secret.

Miranda’s detention was a blatant act of political intimidation, sanctioned at the highest levels by London and Washington. Their aim is to silence any further disclosure of the mass illegal surveillance operations conducted by their spying agencies, as revealed by Snowden.

The illegality of Miranda’s detention was confirmed by Lord Falconer, one of the main architects of the 2000 Terrorism Act. Falconer was a close ally of then Labour Party Prime Minister Tony Blair, under whose government the act was introduced, serving as Solicitor General and later Lord Chancellor.

In a column published in the Guardian Wednesday, Falconer, whilst defending the continued use of schedule 7, added, “There is no suggestion that Miranda is a terrorist, or that his detention and questioning at Heathrow was for any other reason than his involvement in his partner Glenn Greenwald’s reporting of the Edward Snowden story.”

Falconer stated, “Publication in the Guardian is not instigating terrorism. If it is obvious to the state the person detained is not a terrorist, the state must have some purpose other than determining whether he is a terrorist in using the power—and that would render the use of the power unlawful.”

The persecution of Miranda is part of a larger effort by the British state to intimidate those involved in the Snowden leaks and all those opposed to the massive police state being built up in the UK, US and around the world.

Earlier in the week, the Guardian’s editor-in-chief Alan Rusbridger wrote that two months ago, he and other Guardian journalists were faced with unofficial threats of legal action by the British government, and forced to destroy hard drives containing material from Snowden.

The threat had been made by a “senior government official claiming to represent the views of the prime minister”, David Cameron, Rusbridger said. The drives were destroyed in the basement of the Guardian’s office in the presence of spies from Government Communications Headquarters (GCHQ).

On Tuesday the Independent revealed that the senior official was Britain’s top civil servant, Cabinet Secretary Sir Jeremy Heywood.