Bird class patrol vessels
... that Bird class patrol vessels were so unsuccessful that they were never used in their designed role?
... that <b id="mwEXM"><a class="mw-redirect" href="./Bird_class_patrol_vessel" id="mwEXQ" rel="mw:WikiLink" title="Bird class patrol vessel">Bird class patrol vessels</a></b> were so unsuccessful that they were never used in their designed role?