LONDON UNDERGROUND tube map. Under construction to Heathrow. GARBUTT #1 May 1977
The extension to Heathrow Central is shown as being under construction, opening late 1977. Title of map:'London Transport - Diagram of lines - Number 1 1977'. 'London Transport - Diagram of lines - Number 1 1977' (12.76/3239M/1,000,000).