Weren’t UK comedians doing blackface long after it was taboo in the U.S.? I swear I saw a Benny Hill sketch where he was made up that way, although I can’t recall if it’s was the 70’s syndicated version here or the “unexpurgated” versions that ran on cable tv for a time in the early 90’s.

I do recall there was an uproar in the Asian community when the Seller’s movie came out, at least in the states. Peter did a similar accent playing a parody of Charlie Chan in Murder By Death.

I think most of the Imperials sounding British was also influenced by the fact a lot of those same actors played Germans in many World War II movies around the same time.