May briefed before Miranda detained
The Home Secretary has revealed she was briefed in advance of the possible detention of David Miranda at Heathrow Airport.
But Theresa May said that it was not for her to tell the police who they should or should not stop at ports, or who they should arrest.
She said: "If it is believed that 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 is what the law enables them to do."
But the Home Secretary, who has come under pressure to explain how much the Government knew about the planned detention of Mr Miranda after the White House said it had been given a "heads up", said there were safeguards in place to make sure such arrests were conducted properly.
She told the BBC: "I was briefed in advance that there was a possibility of a port stop of the sort that took place. But we live in a country where those decisions as to whether to stop somebody or arrest somebody are not for me as Home Secretary, they are for the police to take, that's absolutely right that they have their operational independence and long may that continue."
Mr Miranda, partner of Guardian journalist Glenn Greenwald, was detained at Heathrow Airport under Schedule 7 of the Terrorism Act 2000 as he changed planes on a journey from Berlin to his home in Brazil.
He claimed he was held for nine hours by agents, who questioned him about his "entire life" and took his "computer, video game, mobile phone, my memory card - everything".
Schedule 7 applies only at airports, ports and border areas, allowing officers to stop, search, question and detain individuals.
Its use has been criticised by Mr Greenwald - the reporter who interviewed American whistleblower Edward Snowden - as a "profound attack on press freedoms and the news-gathering process", and has sparked concern on the use of terror laws.
Mrs May said the Government continued to review counter-terrorism legislation and would be making some changes to Schedule 7 of the Terrorism Act, but said it was an important power, something made clear by both the current independent reviewer of terrorism legislation David Anderson QC, as well as his predecessor Lord Carlile.