BA 34 then FB 852 at Heathrow
Kuala Lumpur → London → Sofia
Timetable, London time
05:20BA 34 from Kuala Lumpur at the gate
17:55FB 852 to Sofia leaves the gate
12 h 35 apart on the timetable
FB 852 leaves 12 h 35 after BA 34 arrives on the timetable: more than half a day, so not a connection we count.