Wordpress is adding this comment above all HTML on my site which is causing problems in IE in which the site won't render properly at all.
How do I stop WP adding this?
Tried disabling all plugins but nothing
I would suggest you to search for files by content and search inside wp-content folder of your WordPress for this string: "page-who-we-are.php" - you'll locate the string and you can remove it.
To search files by content on Windows, see Best way to confidently search files and contents in Windows without using an indexing service?