BA 551 then BA 746 at Heathrow
Rome → London → Geneva
Timetable, London time
15:05BA 551 from Rome at the gate
10:30BA 746 to Geneva leaves the gate
19 h 25 apart on the timetable, overnight
BA 746 leaves 19 h 25 after BA 551 arrives on the timetable: more than half a day, so not a connection we count.