BA 891 then BA 802 at Heathrow
Tbilisi → London → Reykjavík
Timetable, London time
11:50BA 891 from Tbilisi 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 891 arrives on the timetable: more than half a day, so not a connection we count.