A blog on the Dr Who website said that the production team was recreating an iconic scene from a 1964 episode of the sci-fi drama. The Dalek Invasion of Earth saw the alien cyborgs arriving in London and passing the Palace of Westminster.
The BBC tweeted a picture of the original film.
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.
Of all the strange reasons for transport delays - freak snowstorms, the wrong kind of leaves, stray pets - a moving fleet of genetically modified robotic mechanical shells is not usually one of them.
But Transport for London tweeted today: "The filming of Doctor Who has finished at Westminster Bridge, the Daleks are in the process of being removed."
If an invasion of London has begun, the authorities can't be accused of over-reacting.