It was promoted for people attending the London Marathon.
"The easiest way to travel to and from the race is by Tube, Bus, London Overground, Docklands Light Railway (DLR) or Riverboat, however, some stations and roads will be closed, so passengers are advised to plan their journeys in advance by using the dedicated website tfl.gov.uk/marathon or by contacting the 24 hour London Travel Information line on 0343 222 1234. "
http://www.tfl.gov.uk/corporate/media/newscentre/27673.aspx