code was checking diifferent things, one was checking the tracked cookie the other was looking in the database, the two values are slightly diffferent.
There seems to be a discrepency somewhere, although there are in fact no new posts since my last visit in the atached image, the first three posts in the list are displaying the "new posts" icon
The time when I took the snapshot was 20:54, so there should be no posts marked as new!