Penelope Curtis, Director of Tate Britain, said the public have been really patient while the renovations have been underway and she hopes the end result is welcomed.
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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.