Is this usage correct - quite literally at the eleventh hour?

I'm trying to write a sentence which is supposed to mean that something is being done at the last moment.

Sentence - The endleofan gathering was called, when something threatened the very existence of humanity, as an act of last resort,
quite literally at the eleventh hour.

While reading this, it appears that I'm saying that the meeting is occuring at 11 O'clock and not what I intend it to say - "at the last moment when no other options are left".

Is there any way I can make the sentence more clearer, to convey the intended meaning? Feel free to modify the sentence.