BA 541 then BA 420 at Heathrow
Bologna → London → Luxembourg
Timetable, London time
14:30BA 541 from Bologna at the gate
14:00BA 420 to Luxembourg leaves the gate
23 h 30 apart on the timetable, overnight
BA 420 leaves 23 h 30 after BA 541 arrives on the timetable: more than half a day, so not a connection we count.