No, this is not the Southern service, it's Gatwick Express, but why does the information screen tell that it is the Southern service?
Because this timetable represents some of the current services on the Brighton Mainline, in where Southern are using Gatwick Express 387/2s for Southern Services to keep the 387s running while Gatwick Express is temporarily suspended.
Gatwick Express units are also serving some Great Northern services out of Kings Cross, so I wouldn't be surprised to see "Welcome to this Great Northern Service" on those boards IRL
