BA 419 then BA 802 at Heathrow
Luxembourg → London → Reykjavík
Timetable, London time
11:55BA 419 from Luxembourg at the gate
11:45BA 802 to Reykjavík leaves the gate
23 h 50 apart on the timetable, overnight
BA 802 leaves 23 h 50 after BA 419 arrives on the timetable: more than half a day, so not a connection we count.