Be Upfront With Being Let Go if you Applied to the Role Before Getting Fired?

Hey guys,

Curious what your thoughts are, I am going to tell them and have a story for why ready that put's it in a good light. But thoughts on this if the role I'm interviewing for is already somewhat of a long shot (due to other employees pedigree that currently work there) and I let them know.

The risk is I don't say I left and act like I am still there which is very dishonest and I will need to keep up for at least a month if the process gets dragged out. I am 99% telling them what happened, but I wanted to hear from others who didn't and how it went well or didn't go well. Because my last firm can only say he no longer works here right? But I've also heard of people getting fired for not letting the company know they were let go in their last role to HR after being in the new role for 3-4 months.