Jenny Reeves (@Jennyflyer1) was one of the first to post a picture on Twitter.
And Transport for London sounded the all-clear after the "invasion" had been averted.
The filming of Doctor Who has finished at Westminster Bridge, the Daleks are in the process of being removed.
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A retired judge will lead the public inquiry into the Grenfell Tower disaster, the Prime Minister has confirmed.
They tried to drive off, pursued by the suspect on foot, before their car crashed into a fence.
"Three were standing together almost shoulder-to-shoulder in like a little wolf pack and they're staring at me...", said PC Wayne Marques.