BA 242 then BA 746 at Heathrow
Mexico City → London → Geneva
Timetable, London time
13:10BA 242 from Mexico City at the gate
10:30BA 746 to Geneva leaves the gate
21 h 20 apart on the timetable, overnight
BA 746 leaves 21 h 20 after BA 242 arrives on the timetable: more than half a day, so not a connection we count.