TK 1971 then BA 638 at Heathrow
Istanbul → London → Athens
Timetable, London time
16:20TK 1971 from Istanbul at the gate
16:15BA 638 to Athens leaves the gate
23 h 55 apart on the timetable, overnight
BA 638 leaves 23 h 55 after TK 1971 arrives on the timetable: more than half a day, so not a connection we count.