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.
More top news
A drunk man who narrowly escaped death when he lay down between train tracks in Harlow has been given a 12-month community order.
A man from north London has been charged with the manslaughter of Louella Eve Fletcher-Michie, who died at the Bestival music festival.
The mother of Ellie Butler - the six-year-old murdered by her father - has lost a bid to challenge her conviction.