BA 553 then BA 1354 at Heathrow
Rome → London → Saint Helier
Timetable, London time
16:35BA 553 from Rome at the gate
16:20BA 1354 to Saint Helier leaves the gate
23 h 45 apart on the timetable, overnight
BA 1354 leaves 23 h 45 after BA 553 arrives on the timetable: more than half a day, so not a connection we count.