FB 851 then BA 728 at Heathrow
Sofia → London → Geneva
Timetable, London time
12:10FB 851 from Sofia at the gate
08:25BA 728 to Geneva leaves the gate
20 h 15 apart on the timetable, overnight
BA 728 leaves 20 h 15 after FB 851 arrives on the timetable: more than half a day, so not a connection we count.