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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The station, which saw 44m people commuters use it in 2016/2017, will be transformed into a dining room complete with Christmas decorations.
Part of the monster fatberg will go on display in the Museum of London, while the rest of it will be converted into biodiesel.
Major engineering projects at key London stations mean hundreds of trains will be cancelled or diverted.