Comments Not Working on a page

Form the view source of your https://www.usbtastic.co.uk/think-of-a-usb-gadget/ page i can see their is no value for comment_post_ID on that page its blank.

<div class="commentheader">
<h5 id="respond">Leave a Comment</h5>
</div>

<div class="contactform">
<form action="https://www.usbtastic.co.uk/wp-comments-post.php" method="post" id="commentform">

<p>
<label for="author">Name » </label>
<input type="text" name="author" id="author" value="" size="22" tabindex="1" />
</p>

<p>
<label for="email">Email »</label>
<input type="text" name="email" id="email" value="" size="22" tabindex="2" />
</p>

<p>
<label for="url">Website » </label>

<input type="text" name="url" id="url" value="" size="22" tabindex="3" />
</p>

<p>
<label for="comment">Comment » </label>
<textarea name="comment" id="comment" cols="10" rows="10" tabindex="4"></textarea>
</p>

<p>
<label for="submit"></label>
<input name="submit" type="submit" id="submit" tabindex="5" value="Submit Comment" class="submit-button" style="width: 200px;" />
<input type="hidden" name="comment_post_ID" value="" />
</p>

so its bug in your comments.php file or some issue with that page, can you check from your wordpress admin panel wether that post/page has any post_id or not ??

Thanks for your help and diagnosing the problem, I took a closer look at the page and compared it to an original and found I missed 2 lines of code;

<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
and
<?php endwhile; endif; ?>

Thanks again.