Attorneys for David Miranda, the partner of Guardian journalist Glenn Greenwald, are threatening legal action against the British government over Miranda’s detention at London’s Heathrow Airport. Miranda was held for nine hours under a British antiterrorism law. He faced repeated interrogation and had his belongings seized. On Tuesday, Miranda’s lawyers asked the British Home Office to apologize and return his possessions or face action in court. Speaking upon his return to Brazil, Miranda said he was subjected to “psychological violence.”

David Miranda: “A Brazilian that travels to a country like this and is detained for nine hours in this way, it, I think, breaks a person, you understand? You break down completely and get very scared. They didn’t use any physical violence against me, but you can see that it was a fantastic use of psychological violence.”

The British government continues to defend Miranda’s detention. Speaking to the BBC, British Home Secretary Theresa May said Miranda may have been carrying information useful to terrorists.

Theresa May: “I think it’s right, given that it is the first duty of the government to protect the public, that if the police believe somebody has in their possession highly sensitive, stolen information, which could help terrorists, which could lead to a loss of lives, then it is right that the police act. And that’s what the law enables them to do.”

Citing a “U.S. security official,” Reuters reports that in detaining Miranda the British government was trying to “send a message [that it’s] serious about trying to shut down [Snowden’s] leaks.”