BA 349 then A3 603 at Heathrow
Nice → London → Athens
Timetable, London time
21:05BA 349 from Nice at the gate
16:35A3 603 to Athens leaves the gate
19 h 30 apart on the timetable, overnight
A3 603 leaves 19 h 30 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.