BA 633 then BA 257 at Heathrow
Athens → London → New Delhi
Timetable, London time
18:55BA 633 from Athens at the gate
18:35BA 257 to New Delhi leaves the gate
23 h 40 apart on the timetable, overnight
BA 257 leaves 23 h 40 after BA 633 arrives on the timetable: more than half a day, so not a connection we count.