"Colonial functionaries had to learn the major language of their territory at a formidable level. A kitchen jargon, good enough for wives, with bad grammar and a master-race pronunciation, was usually preferred by the natives, who did not believe it was possible for a foreigner with a white skin to learn their language. Colonial civil servants had to disconcert these natives with a linguistic mastery, including a control of many registers, equal to, or greater than, their own. In Malaya, there were many languages, but Malay was considered, for political reasons, to be the obligatory specialisation. You could, if you were mad enough, learn Hakka or Cantonese or Kuo-Yu or Tamil or Hindi or Urdu, but you had to take examinations in Malay. You had to take the Standard One examination in your first year and the Standard Two before the end of your first three-year tour. If you failed, an efficiency bar was invoked, and you were not entitled to annual pay increments."
Burgess was by his account unusually competent linguistically, passing Standard Two by the end of his first year (which made him, he says, disliked) and Standard Three by the end of his tour (which made him hated).
[Edit: Burgess write of his first boss in Malaya that "During the war he had had the chance to learn Japanesr, and he had been sent on a course with fine amenities, including recording apparatus. He had used this apparatus for recording popular songs. I id not think this funny."]
Years ago, I read in a book or magazine article that the British Imperial service was actually quite strong when it came to language instruction. In Malaya, as I recall, they were able to teach officers Cantonese, Hokkien, and other Chinese dialects that are quite hard for non-native speakers to master. I assume that the diplomatic service was similarly effective when it came to training their officers in the languages required to carry out their overseas missions.
So, British officials were able to learn foreign languages, including obscure Asian languages used in their colonies. Yet Japanese was not considered a priority, even though Japan had been regarded as an expansionist regional power for decades (which every Western colonial power was aware of, thanks to Japan's concessions in China, its puppet state in Manchuria, and other militaristic activities/ambitions in the 1920s and 1930s).