BA 673 then QR 16 at Heathrow
Thessaloniki → London → Doha
Timetable, London time
21:45BA 673 from Thessaloniki at the gate
21:30QR 16 to Doha leaves the gate
23 h 45 apart on the timetable, overnight
QR 16 leaves 23 h 45 after BA 673 arrives on the timetable: more than half a day, so not a connection we count.