One of my Members Academy students, Aruzhan, sent me this excellent question this morning, after seeing someone on Instagram say that it is wrong to end a sentence with a preposition.
Although I agree that, in FORMAL WRITTEN English it is technically incorrect to end a sentence with a preposition, it often sounds over-formal in most writing contexts.
In the famous Churchill quote above, he makes fun of the formal rule, using the phrasal verb "to put up with something" (= to tolerate) as an example. It sounds ridiculous when he tries to avoid putting the prepositions "up with" in the middle of the sentence, rather than at the end.
He says it's a kind of "pedantry" (great word!)
a pedant (noun, countable) = a person who is excessively concerned with minor details and rules or with displaying academic learning.
pedantic (adjective) = excessively concerned with minor details or rules
pedantry (noun, uncountable) excessive concern with minor details and rules.