The barrier at King's Cross

The school train leaves from the real King's Cross station, through a barrier the stories place between platforms nine and ten. The number people repeat — nine and three-quarters — is the platform on the far side, not a track you can find on a commuter map.

The image does a lot of work in a few steps. A public station, a family, a moment of disbelief, then a scarlet train. It is the door between the ordinary city and the school year.

Fans still photograph the station's tourist plaque. That plaque is a real-world souvenir of a fictional door. This journal keeps the two separate.