BA 349 then AC 861 at Heathrow
Nice → London → Vancouver
Timetable, London time
21:05BA 349 from Nice at the gate
14:30AC 861 to Vancouver leaves the gate
17 h 25 apart on the timetable, overnight
AC 861 leaves 17 h 25 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.