BA 457 then BA 802 at Heathrow
Madrid → London → Reykjavík
Timetable, London time
11:50BA 457 from Madrid at the gate
11:45BA 802 to Reykjavík leaves the gate
23 h 55 apart on the timetable, overnight
BA 802 leaves 23 h 55 after BA 457 arrives on the timetable: more than half a day, so not a connection we count.