What happens to the other person in the affair?
Since it is a fortune 500 company she will be given a sizable bonus and quietly lead out a side door. I have witnessed this phenomena at every company that I have been employed. Typically a senior V.P. who starts dating a much younger staff member. The rumors begin then pretty soon the whole company knows. The V.P. is shown the door and then 6 month's later the young staff member disappears quietly in the night.
I guess when something like this happens in a company where it is forbidden, one of the people should find another job.