In message , Paul Corfield
writes

Funny that years ago the Piccadilly Line used to run only as far as
Hounslow West and everyone was kicked off on to a bus to get to
Heathrow.

But hardly anyone took that route to Heathrow in my experience.

Before the Piccadilly Line extension, if you weren't travelling to
Heathrow by cab or car you would normally check in at the West London
Air Terminal in Cromwell Road. You and your luggage would then be taken
by BEA (or BOAC) coach down the A4 (and later the M4) to the appropriate
terminal building at Heathrow. Prior to 1957 I believe the check-in was
at Waterloo, although the onward journey was still by airline coach.

--
Paul Terry