BA 194 then BA 418 at Heathrow
Houston → London → Luxembourg
Timetable, London time
06:50BA 194 from Houston at the gate
06:05BA 418 to Luxembourg leaves the gate
23 h 15 apart on the timetable, overnight
BA 418 leaves 23 h 15 after BA 194 arrives on the timetable: more than half a day, so not a connection we count.