Delete from X where Y

I've been trying to find out how to delete data within a model using something like :

$this->delete( array( 'conditions' => 'email = :email: and entity_type = :entity_type:', 'bind' => array( 'email' => $email, 'entity_type' => $entityType ) ) );

maybe with a return type of int which contains the number of records deleted.

It is madness to do a select, then iterate over the result set and delete records individually, as it says in the documentation.

Can someone put me out of my misery and tell me what I am missing here!!!

Thanks. Mark