Cosmic Hobo

"Cosmic Hobo" was a code name given by the British Army to an alien time traveller with a time machine shaped like a police box who went by a title that started with the letter "D". (PROSE: Beast of Fang Rock) The name was devised by Ian Gilmore and Oliver Hamilton; (PROSE: The Enfolded Time) it originated from the fact that several witnesses described the time traveller as being dressed like a hobo. The "Hobo" was often accompanied by young assistants. (PROSE: The Dogs of War)

Some reports suggested that the name "Cosmic Hobo" was a code name for was itself another code name used by multiple individuals. While most accounts of the "Cosmic Hobo" described him as being short and dark-haired, some witnesses described a different-looking old man. (PROSE: The Dogs of War) The "Hobo" was sometimes mistaken to be a medical doctor. (PROSE: Beast of Fang Rock)

By mid-1969, there were at least five documented sighting of the "Cosmic Hobo" dating back to the 1940s; these included: Northumberland in 1943, South Wales in 1959 , (PROSE: Beast of Fang Rock) during the encounter ICMG had with alien battle machines in Shoreditch in 1963 , (PROSE: The Dogs of War) at Gatwick Airport in 1966 , (PROSE: The Dogs of War, Beast of Fang Rock) and during the London Event of 1969. (PROSE: Beast of Fang Rock)

Undocumented incidents involving the "Hobo" included the Great Intelligence's attack on the Det-Sen Monastery in 1935 and the Rutan scout incursion at the Fang Rock lighthouse in 1902. (PROSE: Beast of Fang Rock)

After Anne Travers and Alistair Gordon Lethbridge-Stewart met the "Cosmic Hobo" during the London Event, they were required to sign the Official Secrets Act - the Act required them to not refer to the "Cosmic Hobo" by his real name. Travers recommended that Lethbridge-Stewart train his mind to think of the time traveller as the "Cosmic Hobo". (PROSE: Beast of Fang Rock)

During the Grandfather attack on Earth, McMillan inquired into Lethbridge-Stewart's previous encounters with extraterrestrials but was not able to find much information about Alistair's first alien encounter due to the involvement of the "Cosmic Hobo". (PROSE: The Grandfather Infestation)

However, in the 1970s the "Cosmic Hobo" underwent a drastic change which resulted in the description of him being a cosmic hobo no longer being very applicable. The code name was dropped and forgotten. (PROSE: The Enfolded Time)

Behind the scenes

 * Although legal matters prevented this from being made explicit, it is quite clear to readers that one is meant to assume the "Cosmic Hobo" is none other than the Second Doctor, "cosmic hobo" being a popular description of the character's look in the real world. As such, the "drastic change" which makes the description unsuitable is likely the Second Doctor's regeneration into the third, who famously dressed not like a hobo but like a glamorous gentleman.