Now frowned upon! I used this for a Shuttle last year (or OO... operations other, apparantly) and was told under no uncertain circumstances to ever use it again, as it was for Heathrow's use only!
I've used it umpteen times before working for The World's Favourite Airline, but I seem to recall the most bizarre was during severe snow at Glasgow during March 2006 when a Captain who shall remain nameless other than as "Delay 60", got into an arguement with his management as he was convinced he was going to AMS, not AGP, and that all the paperwork he was presented with was wrong...
... dunno what was more worrying to be honest, the fact he swore black was blue that he was right, or the fact that the airline let him go to AMS!