BA 551 then BA 574 at Heathrow
Rome → London → Milan Linate
Timetable, London time
15:05BA 551 from Rome at the gate
14:55BA 574 to Milan Linate leaves the gate
23 h 50 apart on the timetable, overnight
BA 574 leaves 23 h 50 after BA 551 arrives on the timetable: more than half a day, so not a connection we count.