BA 681 then BA 253 at Heathrow
Istanbul → London → Grand Cayman
Timetable, London time
09:50BA 681 from Istanbul at the gate
09:35BA 253 to Grand Cayman leaves the gate
23 h 45 apart on the timetable, overnight
BA 253 leaves 23 h 45 after BA 681 arrives on the timetable: more than half a day, so not a connection we count.