SK 809 then BA 638 at Heathrow
Oslo → London → Athens
Timetable, London time
16:25SK 809 from Oslo at the gate
16:15BA 638 to Athens leaves the gate
23 h 50 apart on the timetable, overnight
BA 638 leaves 23 h 50 after SK 809 arrives on the timetable: more than half a day, so not a connection we count.