Air Traffic Control, like aviation generally, learns from and responds to serious incidents. Chris Stock has sent in two pivotal early incidents from the late 1940s that I’ve provided links to.
G-AHCW 19 Feb 1949 Dakota at Exhall
SE-BDA 4 July 1948 DC-6 Northolt
An archive of 20th century air traffic control photographs and other media sponsored by the Guild of Air Traffic Control Officers http://gatco.org/