Orient Express

The Orient Express was the name of a long-distance passenger train originally operated by the Compagnie Internationale des Wagons-Lits on Earth.

History
The two city names most intimately associated with the Orient Express were Paris and Istanbul, the original endpoints of the service. In 1887, Sherlock Holmes and Dr. Watson were riding on the Express through Austria when they were stopped by the train of Pope Leo XIII, who commissioned Holmes to investigate the disappearance of books from the Library of St John the Beheaded in London. (PROSE: All-Consuming Fire)

The train was perhaps most famous for being the setting of a detective novel, Murder on the Orient Express, written in 1934 by Agatha Christie and featuring her Belgian detective character Hercule Poirot. This was inadvertently inspired by Donna Noble, when she met the writer in 1926. It is unlikely, however, that, per Donna's suggestion, the book was copyrighted "Donna Noble." (TV: The Unicorn and the Wasp)

At an unknown time, an Orient Express was in space, having trouble with an "Egyptian Goddess" who had escaped from the Seventh Obelisk. A king or queen called the Eleventh Doctor to come and help. (TV: The Big Bang)

According to BBC's freshly-released Series 8 episode list, "Mummy On The Orient Expres", the 8th episode, is set to continiue the story behind the call in Series 5.