not for one instant

not for one instant

Not for any length of time; not at any point; not at all or in any capacity. Not for one instant did I think this would be a winning ticket, so I was totally gobsmacked to find out I'd won the jackpot! A: "So, did you suspect we were throwing you a surprise party?" B: "No, not for one instant!"
See also: instant, not, one
Farlex Dictionary of Idioms.

not for a/one ˈminute/ˈmoment/ˈsecond/ˈinstant

(informal) not at all; definitely not: I didn’t think for a minute that he was married. Not for one instant would I ever consider going there on holiday again.
See also: instant, minute, moment, not, one, second
Farlex Partner Idioms Dictionary
See also:
  • not for a instant
  • not for a/one minute/moment/second/instant
  • not for a second
  • not for a minute
  • not for a moment
  • aint
  • ain't
  • (I) hope not
  • hope not
  • be like ships in the night
References in classic literature
Cornelius started back in dismay, when in the thief, in the pretended Jacob, he recognised his neighbour, Isaac Boxtel, whom, in the innocence of his heart, he had not for one instant suspected of such a wicked action.
The idea of renewing my labours did not for one instant occur to me; the threat I had heard weighed on my thoughts, but I did not reflect that a voluntary act of mine could avert it.
But we never forget, and I mean not for one instant, that we are helping our clients to make themselves more successful.
"He has not for one instant yielded up to that malign intent.
Yet the book is not for one instant either mawkish or morbid."