BA 631 then BA 410 at Heathrow
Athens → London → Valencia
Timetable, London time
17:00BA 631 from Athens at the gate
16:50BA 410 to Valencia leaves the gate
23 h 50 apart on the timetable, overnight
BA 410 leaves 23 h 50 after BA 631 arrives on the timetable: more than half a day, so not a connection we count.