Wiktionary
under no circumstance
adv. In no case, whatever happens; never.
Usage examples of "under no circumstance".
The President had said, firmly, that under no circumstance was she to go with him to Fort Stevens, while Lamon had said that under no circumstance would he allow the President to return to Fort Stevens.
Moreover, every citizen's station in the society is fixed since birth, and under no circumstance is someone from the unworthy lower class permitted to ascend to higher positions.