Remember that most european airlines will fly at least one BIG plane into LHR (usually at about 9 in the morning)…SWISS (MD11/A330), KLM (767 usually), etc do this… so maybe Iberia are just catching on? wouldnt be a^bad idea to just do a quick “turnaround” in MAD and send it on its way down south, since im guessing most of the passengers are transit to LatAm anyways…
and TAP used to fly the A340 into GVA back in 1994/95 on a regular basis, so it waouldnt really surprise me to see it at LHR