Originally Posted by
MatthewLAX
Especially when the red buses are free...
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Great trip report lorelai!
It all depends on the OP's circumstances - loads of luggage, mobility issues, time pressure etc could all make a taxi the best option.
Also If I remember correctly there is a tunnel leading from the Heathrow Hilton directly into T4. From there you can take the Heathrow Express free to T5 or pay around £3 to take the tube.