BA 16 then FB 852 at Heathrow
Sydney → London → Sofia
Timetable, London time
05:25BA 16 from Sydney at the gate
17:55FB 852 to Sofia leaves the gate
12 h 30 apart on the timetable
FB 852 leaves 12 h 30 after BA 16 arrives on the timetable: more than half a day, so not a connection we count.