Boris Johnson has announced a £1.5 billion project to develop the 50 acre site in Silvertown Quays in a scheme that could create up to 9,000 jobs.
The area has been undeveloped for decades but the developers behind the scheme The Silvertown Partnership say London has seen the regeneration of a number of sites across East London such as nearby Canary Wharf and Straford.
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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.