HD... over on abix we've nailed down the date for the official name change from London Airport (L.A.P) to London Heathrow Airport as between 1January and 1April 1961 with a corresponding change from Gatwick Airport to London Gatwick Airport. The codes changed from LON to LHR and GWK to LGW by March 1963 apparently. So presumably the Tower switched from being 'London' to 'Heathrow' on the official date? Would there have been any confusion between the Tower name and the Area name back then?