comment author link to phpBB profile

I’ve converted my phpBB database of users so that all the columns are compatible with WP, essentially setting myself up to use the wphpbb login plugin.
So now all the user IDs are sync’d, what does this mean?
Well you can use the author_ID to link a persons name to their profile like so
http://example.com/phpBB2/profile.php?mode=viewprofile&u=<?php author_ID ?>
however this only works for authors as I can not find a comment_author_ID tag.
Obviously if the person wasn’t logged in when they commented I’d have an ‘if’ statement to do something else but the point remains.

Any ideas how I could do it, just so that wordpress is involved that little bit more with phpBB?