I remember seeing it from Kew Gardens on approach in September '75, doing route proving I believe. My first sighting...
Just trying to recall the transports I saw at Heathrow between early '75 and 1984 when my occasional spotting daytrips ended.
Viscount, VC-10, Vanguard, Herald, 1-11, F-27, F-28, A300/310, 707, 727, 737, 747, 757, 767, DC-6, DC-8, DC-9, DC-10, Electra, Tristar, Caravelle, HS748, Beech 99, IL-18, IL-62, CL-44, Tu-134, Tu-154, IL-86?, VFW-614, DHC-7, Metroliner, C-130, Concorde, S-61N, Argosy - 36 distinct types, plus execs and the odd lighter aircraft (eg Air Anglia PA-31s).
Two summers ago, spent a morning there with a mate:
B737, 747, 757, 767, 777, 787, A320 family, A330, A340, A380, ummmmm. Maybe Bombardier and Embraer types...