IB 721 then KL 9936 at Heathrow
Madrid → London → Amsterdam
Timetable, London time
17:15IB 721 from Madrid at the gate
14:27KL 9936 to Amsterdam leaves the gate
21 h 12 apart on the timetable, overnight
KL 9936 leaves 21 h 12 after IB 721 arrives on the timetable: more than half a day, so not a connection we count.