Some will reject you on the basis of age, even if they don't say so for legal reasons.
I guess the issue is what you've done with the last 20 years and what you want to do.
An MBA + MSc in S/W eng does not imply to me that you've done the right maths and IT consultancy does not set and expectation that you've done it since, but feel free to correct me.
The role you're going for would be a quant developer and the lower bound of maths for that is not very high but to make it a success more is better.
When I've pitched older candidates I've taken the ageism on from the front, and said "treat this guy as a new grad who '
just happens' to have the sort of skills you'd expect from a decade of
C++"
Note the
C++ hook there, you'd be a programmer maybe a better paid one than you are now, but essentially starting near the bottom of that particular pile. You need to be clear in your own mind that this is something you'd be happy with, maybe that's where you stay, maybe not..
So this can work if you want to cut code and have adequate maths to get the right sort of code written.
In terms of selling yourself, one thing that managers at banks are usually concerned about is "professionalism" in their s/w development for which the average is poor and the first moment is really quite scary. You can pitch yourself as someone who will bring professionalism and maturity to the QuantDev work in terms of process and robustness (assuming this to be true of course).
An extra point is that the 20 years must look successful, even if not finance related, it's hard to sell a refugee.
