London prices have risen by 10.9%, according to latest Land Registry figures, the fastest rate since July 2010.
The average price of a home in the capital now stands at £409, 881.
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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.