London, or Londinium, was a city in River Song's World.
It was similar to London from the Doctor's World, except that all of its history was occurring at once. Trains passed through a counterpart of the Gherkin, while pterodactyls flew over Hyde Park. The Buckingham Senate was also located in the city.
Media outlets included the BBC and the Londinium Cotide.
The Eleventh Doctor, known locally as the Soothsayer, was imprisoned in the Tower of London. Winston Churchill ordered that he be brought to the Buckingham Senate to explain why the time never changed: it was stuck at 5:02pm on 22 April 2011.
When the Eleventh Doctor and River Song made physical contact, the timeline was aborted and, along with the rest of River Song's World, this version of London was erased. (TV: The Wedding of River Song)