Labour's Tom Copley asks about families being evicted or moved because of benefit reforms. @itvlondon
Johnson: talks of "eyewatering sums" of benefit - "Not everybody can live exactly where they want in London." @itvlondon
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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.