BA 553 then TK 1934 at Heathrow
Rome → London → Istanbul
Timetable, London time
16:35BA 553 from Rome at the gate
16:00TK 1934 to Istanbul leaves the gate
23 h 25 apart on the timetable, overnight
TK 1934 leaves 23 h 25 after BA 553 arrives on the timetable: more than half a day, so not a connection we count.