London's Transport Commissioner, Peter Hendy CBE said:
"With London's population forecast to grow by one million people in the next 20 years, it is essential that we continue to invest in making our network more reliable and that we enable the London and UK economy to grow and prosper in the years ahead."
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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.