BA 879 then BA 854 at Heathrow
Bucharest → London → Prague
Timetable, London time
10:10BA 879 from Bucharest at the gate
09:45BA 854 to Prague leaves the gate
23 h 35 apart on the timetable, overnight
BA 854 leaves 23 h 35 after BA 879 arrives on the timetable: more than half a day, so not a connection we count.