BA 1421 then BA 636 at Heathrow
Inverness → London → Athens
Timetable, London time
13:25BA 1421 from Inverness at the gate
13:10BA 636 to Athens leaves the gate
23 h 45 apart on the timetable, overnight
BA 636 leaves 23 h 45 after BA 1421 arrives on the timetable: more than half a day, so not a connection we count.