BA 477 then BA 836 at Heathrow
Barcelona → London → Dublin
Timetable, London time
14:05BA 477 from Barcelona at the gate
17:20BA 836 to Dublin leaves the gate
3 h 15 apart on the timetable
The last days
BA 477 and BA 836 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.