SevenHeavy From United Kingdom, joined Mar 2004, 1137 posts, RR: 10 Reply 19, posted (5 years 10 months 4 weeks 4 hours ago) and read 9530 times:
All I can say is that it was not a VS aircraft. They never park on the south side by T4 or the cargo "sheds".
Even if it was VS there are no aircraft in the fleet painted in a special livery which feature green anywhere on the fuselage.
My best guess is that there are a couple of private A340 that fly into LHR frequently. Could be one of those. They invariably park right where you are describing - I'll try and find a couple of pictures.