DL 58 then BA 870 at Heathrow
Boston → London → Budapest
Timetable, London time
06:50DL 58 from Boston at the gate
19:25BA 870 to Budapest leaves the gate
12 h 35 apart on the timetable
BA 870 leaves 12 h 35 after DL 58 arrives on the timetable: more than half a day, so not a connection we count.