AC 888 then SQ 305 at Heathrow
Ottawa → London → Singapore
Timetable, London time
09:20AC 888 from Ottawa at the gate
09:10SQ 305 to Singapore leaves the gate
23 h 50 apart on the timetable, overnight
SQ 305 leaves 23 h 50 after AC 888 arrives on the timetable: more than half a day, so not a connection we count.