Originally Posted by
harryhv
Heathrow airport doesn't provide any sensible transfer between T5 and T4. The trains are intermittent and the journey will take up to an hour though there's no problem with baggage.
The trains run to a 'clockface' timetable and, even if the stars are completely misaligned, it's really likely to be only 40 minutes between T5 & T4 - including waiting time.
It is, admittedly, a ridiculous amount of time considering the distance, but if you're not in a particular hurry and just want lifts/level access, it's reasonably pain-free.