In a final week of witness hearings at the Leveson inquiry, Sue Akers, the officer in charge of investigations into alleged phone hacking and corruption of public officials has stepped up to the witness box.
Deputy Assistant Commissioner Sue Akers says that the Metropolitan police believes another prison officer has received £14,000 in payments from Trinity Mirror and that her force have seen articles in the Daily Mirror which it believes relate to these payments.
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The threat level has been raised to critical by MI5's Counter-Terrorism Analysis Centre.
Prime Minister Theresa May announced the decision from Downing Street.
A man, apparently armed with a small axe and a large stick, was detained close to the event and police cleared the area as a precaution.