How part of Hong Kong became ruled by China overnight

China has, for the first time, taken over jurisdiction of a part of Hong Kong - a section of a new high-speed rail terminal.

The exchange happened in a secret, midnight ceremony which made the area subject to Chinese rather than Hong Kong law.

Hong Kong-based journalist Mary Hui explains what's in it for both sides.

(Photo: A worker walks past a line dividing Hong Kong (L) and the mainland Chinese control zone. Credit: Getty Images)