Business leaders say night flights into London's airports must be protected because they are a vital part of the economy.
They were responding to a Department for Transport consultation ending today on current night flying operations at Heathrow, Gatwick and Stansted.
This report from our Political Correspondent Simon Harris.
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Paramedics were on standby outside the police cordon as armed officers stood by the property.
A team of researchers has taken samples from the ten busiest London Underground lines to work out which are the dirtiest.
The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.