 FACT: According to the book, Hogwarts students reach the train by  going through platform no. 9¾, which is secretly located in the  barrier between platforms 9 and 10. In reality, platforms 9 and 10  are in separate buildings, and there is no barrier between them, but  railway tracks. People wrote to Rowling about this, and she admitted  getting confused between Kings Cross and Euston stations. The  Platforms actually used in filming are platforms 4 and 5.