Thing is, it really doesn't matter too much what shape the actual helipad is, be it round, square, triangular or just an "H" marked on the surface.
Sid, did you really think I was confused by a triangular landing marking? Did you not read or understand my second paragraph (the one that begins
"Seriously though...."), or did you just deliberately choose to ignore it?
And seriously, do you really believe that any professional helicopter pilot regularly operating out of UK's busiest airport could do so without reading the relevant AIP entry before? By the way, the first photo of LHR you posted is very much out of date (Yes, I know it's a cut and paste from Google earth).
