6 months before I arrived at my first posting as a ground eng at Northolt a Panam 707 landed at Northolt mystifying Heathrow tower when the pilot announced he had landed and requested taxi instructions!
Now far be it for me to Poo poo this story as fantasy but the story has been repeated over a number of years from different sources.
Absolutely true. The two gasometers concerned were at South Harrow and Southall. As far as I recall, coming over Harrow Hill the South Harrow gasometer lined you up nicely for Northolt, the Southall one for Heathrow. I can personally recall a very low fly-by of my parents' house in South Harrow sometime in the mid- to late-1960s by a Swissair DC8 who nearly made the same mistake but realised in the nick of time and exited stage left on full power amidst much smoke and noise!
That's why the South Harrow gasometer now bears a large NO↑ and the Southall one an equal sized LH↑.
GG