Well it's a legal requirement assuming it was a flight originating from an eligable European Destination (I'm guessing you're referrring to 9W 115 from LHR here per your other post) and it arrived suitably late (3hrs+), and was for a reason within the airlines control.

But I've only ever had long delays the other way (India to Europe) which on non-EU carriers like Jet, aren't eligible, so I'm not going to be any help on this one unfortunately. Someone else might have, but this isn't a particularly busy forum here on FT.