BA 483 then BA 257 at Heathrow
Barcelona → London → New Delhi
Timetable, London time
19:25BA 483 from Barcelona at the gate
18:35BA 257 to New Delhi leaves the gate
23 h 10 apart on the timetable, overnight
BA 257 leaves 23 h 10 after BA 483 arrives on the timetable: more than half a day, so not a connection we count.