BA 349 then BA 862 at Heathrow
Nice → London → Prague
Timetable, London time
21:05BA 349 from Nice at the gate
17:20BA 862 to Prague leaves the gate
20 h 15 apart on the timetable, overnight
BA 862 leaves 20 h 15 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.