Routes / Prefix

How do I not include a prefix in a link?

 

I am at a prefixed url www.site.com/admin/settings and on that page there is “home” which is <?php echo $this->Html->link('Home, array('controller' => 'posts',' action' => 'index' , 'prefix' => false), array('escape' => 'false'),false); ?> but it shows www.site.com/admin/posts

 

Any ideas how to remove prefix’s from a non prefixed link?

 

Thanks,

Dave