Thanks mate,
Your help led me to this:
loop-single.php
<?php if (has_post_thumbnail() ) : ?>
<div id="post_header_img">
<h1 class="entry-title"><?php the_title(); ?></h1>
<div>
<?php else :?>
<?php endif; ?>
<h1 class="entry-title"><?php the_title(); ?></h1>
<?the_post_thumbnail(); ?>
It just weird how the <?the_post_thumbnail(); ?> has to be outside the if and else tag for the result I want… but it works.
You can now view a post with a featured image and without.
https://www.antoniodigitalmedia.com/2012/08/14/this-is-my-tuttle/
https://www.antoniodigitalmedia.com/2012/08/14/225/
Many thanks
