Not only were delays in 2012/13 lowest on record, but the last year has also been the busiest for the capital's tubes. Transport for London says one of the contributing factors was the Olympics, boosting the number of journeys to one point two billion.
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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.