correct English

The answers are below - with the caveat "that opinions about what is 'correct' English have changed a lot over the last 110 years".

The correct English version is, “The favor of a reply is requested.”

Another of Poirot's trademarks is his occasional struggle to find the correct English word or idiom.

"Despite the Brexit I decided to come here because I wanted to learn to speak correct English, not American or Australian English," he said.

In a recent study, linguist Evan Bradley asked people to judge the grammar of sentences with a singular “they” as “correct English” or not.