BA 631 then BA 95 at Heathrow
Athens → London → Montréal
Timetable, London time
17:00BA 631 from Athens at the gate
16:45BA 95 to Montréal leaves the gate
23 h 45 apart on the timetable, overnight
BA 95 leaves 23 h 45 after BA 631 arrives on the timetable: more than half a day, so not a connection we count.