A3 602 then BA 746 at Heathrow
Athens → London → Geneva
Timetable, London time
15:30A3 602 from Athens at the gate
10:30BA 746 to Geneva leaves the gate
19 h apart on the timetable, overnight
BA 746 leaves 19 h after A3 602 arrives on the timetable: more than half a day, so not a connection we count.