BA 633 then BA 546 at Heathrow
Athens → London → Bologna
Timetable, London time
18:55BA 633 from Athens at the gate
18:10BA 546 to Bologna leaves the gate
23 h 15 apart on the timetable, overnight
BA 546 leaves 23 h 15 after BA 633 arrives on the timetable: more than half a day, so not a connection we count.