BA 349 then BA 1099 at Heathrow
Nice → London → Toronto
Timetable, London time
21:05BA 349 from Nice at the gate
17:15BA 1099 to Toronto leaves the gate
20 h 10 apart on the timetable, overnight
BA 1099 leaves 20 h 10 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.