The 200

The 200 was an ordinary London double-decker bus that made an extraordinary detour through a wormhole to the planet San Helios in April 2009. It accepted Oyster cards as payment for trips, though the scanner was fooled by the Doctor's psychic paper.

History
When the transit through the wormhole took place, the 200 had eight occupants, including the Tenth Doctor, the fugitive Christina de Souza (who evaded the police by hopping on the 200 bus) and its driver, who was killed when he attempted to run through the wormhole, but was incinerated. It was running an evening service bound for London Victoria station via Vauxhall, Oval and Brixton. The bus's number plate was W974 GHM. The other five passengers were Angela Whittaker, Nathan, Barclay, Carmen and Lou.

A small party of Tritivores who had crashed on San Helios mistook the 200 for a weapon. The bus took the brunt of the wormhole's power to protect its occupants but was badly damaged as a result, losing much of the left side of its top deck. It was left stuck in the sand, and though the passengers atttempted to dig it out sufficiently to allow it to reverse through the wormhole using duckboards improvised from its upholstery, it ran out of petrol and was effectively marooned, however, so the Doctor fitted it with anti-gravity clamps from the Tritovore ship to fly it through the wormhole, back to London. However, the 200 was pursued by the ravenous Stingrays, which were shot down by soldiers. Back on Earth, Lady de Souza took advantage of a distraction and the Doctor's secret help to steal the bus and escape in it, flying away. (TV: Planet of the Dead)

Later, during his eleventh incarnation, the Doctor said that the Timeship had created a rift large enough to drive a double-decker bus through, and mentioned that he had actually done so before. (PROSE: Paradox Lost)

Behind the scenes

 * The number 200 commemorated the two hundredth Doctor Who story aired on television, Planet of the Dead. The real-world bus route 200 does not terminate at Victoria. It runs from Raynes Park to Mitcham via Wimbledon.
 * The damage done to the bus when going through the wormhole in the story was not intentional — on 8 January 2009, word reached the production team that a transportation mishap had resulted in the bus, which was being shipped to Dubai for use in location filming, being heavily damaged in an accident involving a crane in Turkey. Russell T Davies convened an emergency meeting to discuss how to proceed. As it gave the impression of damage and showed how dangerous the wormhole actually was, instead of repairing the bus, the damage was written into the script, and it was touched up to look burned as well as gashed. (REF: Doctor Who: The Writer's Tale - The Final Chapter)