> and travellers will be able to go from London to Constantinople in forty hours
By the 1930s, Constantinople been a long time gone. It had been Istanbul not Constantinople for centuries by that point.
The formal Ottoman name was Kostantiniyye=Constantinople until the empire's fall in 1922. The official shift happened in 1930, with the Turkish Postal Services Law changing the name to Istanbul.
That's nobody's business but the Turks. Why did Turkey become Türkiye but Japan didn't become Nippon (or vice-versa!)? It's all very confusing to me.
It was the official name of Istanbul up until 1930 (in Turkish, Kostantiniyye).
Why did Constantinople get the works?
Many nations/languages did not respect that rename until Turkey became an ally in the 20th century.