"The Control Tower at Croydon handles daily over sixty air liners. All are given frequent weather reports and the position of other aircraft on their route. In bad visibility, pilots are given their position by wireless. Inside the Control Room, Air Ministry officials plot the position of each aircraft and flag them on the chart. The risk of collision is thus eliminated.
"Companies operating from Croydon include Air Despatch, Wrightways, Olley Air Services and Air Taxis Ltd"
Source: "Modern Wonder", 1938