Return column title if value present

Right, apologies, I have let my excel skills suffer through lack of use. This hsould be easy.

ROW 1 - list of headings
ROW 2 - blank cells that may contain an "X"

At the end of Row 2 I want it to find out which is the last column with an "X" in it, i.e. F2, and return the title of that column, i.e. F1.

Any ideas?