BA 551 then BA 892 at Heathrow
Rome → London → Sofia
Timetable, London time
15:05BA 551 from Rome at the gate
13:25BA 892 to Sofia leaves the gate
22 h 20 apart on the timetable, overnight
BA 892 leaves 22 h 20 after BA 551 arrives on the timetable: more than half a day, so not a connection we count.