BA 631 then BA 990 at Heathrow
Athens → London → Berlin
Timetable, London time
16:30BA 631 from Athens at the gate
16:00BA 990 to Berlin leaves the gate
23 h 30 apart on the timetable, overnight
BA 990 leaves 23 h 30 after BA 631 arrives on the timetable: more than half a day, so not a connection we count.