BA 423 then FB 852 at Heathrow
Málaga → London → Sofia
Timetable, London time
15:00BA 423 from Málaga at the gate
12:55FB 852 to Sofia leaves the gate
21 h 55 apart on the timetable, overnight
FB 852 leaves 21 h 55 after BA 423 arrives on the timetable: more than half a day, so not a connection we count.