I put together a Harry Potter trivia contest yesterday and asked a really bad question. The question was: Who was in King's Cross Station with Harry? I was thinking of Dumbledore and the icky little thing that was part of Voldemort. But KCS is the place where the kids caught the Hogwarts Express at Platform 9-3/4, so the entire Weasley family was there with him, Hermione was there, Sirius Black was there...the list of people is pretty long throughout the entire series. Book 7 ends with another group of people there with him. So it was perhaps the worst trivia question in the history of trivia questions. I like the feeling of accomplishment! LOL
King's Cross is featured in the Harry Potter books, by J. K. Rowling, as the starting point of the Hogwarts Express. The train uses a secret platform 9¾ located by passing through the brick wall barrier between platforms 9 and 10.
Unfortunately, platforms 9 and 10 are in a separate building from the main station; also, rather than being adjacent so that a barrier could be between them, they are separated by two intervening tracks. Rowling intended the location to be in the main part of the station, but misremembered the platform numbering. During an interview in 2001, she indicated that she had confused King's Cross with Euston. In fact, platforms 9 and 10 at Euston are also separated by two intervening tracks, so either she had yet another station in mind or else she simply did not consider or did not remember the physical arrangement of consecutively numbered platforms.
When the movies were filmed, the station scenes took place within the main station, with platforms 4 and 5 renumbered 9 and 10. In the film of Harry Potter and the Chamber of Secrets, the exterior of the adjacent St. Pancras station was used, as its Gothic façade was considered more impressive than the real King's Cross station.
When the first film was released, a large floor panel was placed on the ground outside platforms 9 and 10 indicating the Hogwarts Express. It was later removed. Within King's Cross, a cast-iron "Platform 9¾" sign has been erected on a wall of the station's suburban building containing the real platforms 9 and 10. Part of a luggage trolley has also been installed below the sign; whilst the near end is visible, the rest of the trolley seems to have disappeared into the wall.
"Kings Cross" is the title of the 35th chapter of Harry Potter and the Deathly Hallows, where a location resembling the station plays a significant role. The station is also featured in the epilogue of the same book, making it the final setting of the Harry Potter series.