BA 475 then BA 802 at Heathrow
Barcelona → London → Reykjavík
Timetable, London time
13:10BA 475 from Barcelona at the gate
11:45BA 802 to Reykjavík leaves the gate
22 h 35 apart on the timetable, overnight
BA 802 leaves 22 h 35 after BA 475 arrives on the timetable: more than half a day, so not a connection we count.