"Colin Rosenstiel" wrote

Good grief! I have that booklet (but 2nd impression, 1968) and the rest
of the series published around that time!

How many were there? I've got six, but I don't know whether it's the full
set:
Sixty Years of the Bakerloo (1966)
Sixty Years of the Piccadilly (1966)
Sixty Years of the Northern (1967)
100 Years of the District (1968)
Seventy Years of the Central (1970)
The Metropolitan Line - A Brief History (1972)