Returning families with no right to be in the UK is one of the most difficult and sensitive aspects of our work and we are committed to treating everyone in our care with respect and humanity.
We will consider the recommendations in the HMCIP's report carefully and respond in due course.
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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.