BA 421 then SK 528 at Heathrow
Luxembourg → London → Stockholm
Timetable, London time
19:05BA 421 from Luxembourg at the gate
18:05SK 528 to Stockholm leaves the gate
23 h apart on the timetable, overnight
SK 528 leaves 23 h after BA 421 arrives on the timetable: more than half a day, so not a connection we count.