BA 865 then BA 418 at Heathrow
Prague → London → Luxembourg
Timetable, London time
08:15BA 865 from Prague at the gate
07:40BA 418 to Luxembourg leaves the gate
23 h 25 apart on the timetable, overnight
BA 418 leaves 23 h 25 after BA 865 arrives on the timetable: more than half a day, so not a connection we count.