My first time through must have been 1978, on of all things a BA 747 inbound from Los Angeles. There was a strike in progress at Heathrow, and we landed not to disembark but to reprovision some aspect (not fuel) before continuing after about an hour. The only other aircraft visible I recall was a Ugandan cargo 707 sat in a corner.
Should have been flying out of there yesterday morning as well, but that trip has been lost ...