BA 669 then A3 603 at Heathrow
Marrakesh → London → Athens
Timetable, London time
20:45BA 669 from Marrakesh at the gate
16:35A3 603 to Athens leaves the gate
19 h 50 apart on the timetable, overnight
A3 603 leaves 19 h 50 after BA 669 arrives on the timetable: more than half a day, so not a connection we count.