Using warp tool on mural photo taken from below

[TheDoc]

I have attached a picture of the mural that stands above the auditorium of my high school that I last attended 51 years ago.  Due to the angle that the picture is taken (from center below) it is not it's actual rectangle.  I have tried the warp tool but have not been successful creating a "perfect" rectangle out of the picture. It almost looks like the photo was taken with a fish eye lens. The people surrounding the center pair are actually standing normally and not leaning into the center. Any suggestions?  

[Fixx]

Usually this correction is done in Develop persona > Lens Correction, but this is so extreme distortion that it has to be done otherwise. Mesh warp tool is helpful but even there it takes a lot of fiddling to get it done.

[GarryP]

Welcome to the forums.
A quick play with the Lens Distortion Filter and the Mesh Warp Tool gave me the attached image. (It’s not meant as a perfect example, just to show that something can be done. Image is small so as not to show the low resolution.)
My worry with trying to ‘fix’ your image is that the distortions necessary would be so large that you would lose too much detail, thus making the image useless for most purposes.
Hopefully someone else has a good solution but I think this might be very difficult to do without a lot of very precise manual work. Or maybe there’s a quick fix that I don’t know about – that’s very possible.