The new building will be on the same scale as the huge structure of iron and glass designed by Joseph Paxton for the 1851 Great Exhibition in Hyde Park. It was the largest glass structure in the world before it was destroyed by fire in 1936.
It was later relocated to south-east London to the area which became known as Crystal Palace.
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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.