BA 1337 then SQ 321 at Heathrow
Newcastle → London → Singapore
Timetable, London time
21:55BA 1337 from Newcastle at the gate
21:45SQ 321 to Singapore leaves the gate
23 h 50 apart on the timetable, overnight
SQ 321 leaves 23 h 50 after BA 1337 arrives on the timetable: more than half a day, so not a connection we count.