BA 583 then BA 1376 at Heathrow
Milan → London → Manchester
Timetable, London time
13:30BA 583 from Milan at the gate
18:00BA 1376 to Manchester leaves the gate
4 h 30 apart on the timetable
The last days
BA 583 and BA 1376 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.