Remove 'Private' prefix from pages and posts

I guess I’m tired, because I’m going round in circles here.

I’m trying to remove the ‘Private’ prefix on private posts (and in archive/category view) but I’m struggling a bit.

I had the following pasted into the bottom of my funtions.php file earlier, which I think was working…

function title_format($content) {
return '%s';
}
add_filter('private_title_format', 'title_format');
add_filter('protected_title_format', 'title_format');

… but I’ve migrated to a child theme since then, which might be why it’s not working any more?

I’ve also tried whacking something like this:

<?php
function the_title_trim($title=null)
{
  $title = the_title('','',false);
  $pattern[0] = '/Protected:/';
  $pattern[1] = '/Private:/';
  $replacement[0] = ''; // Enter some text to put in place of Protected:
  $replacement[1] = ''; // Enter some text to put in place of Private:

  echo preg_replace($pattern, $replacement, $title);
}
?>

into my child theme’s style.css file, but that does nothing as far as I can tell.

Anyway, going round in circles. I know there have been previous discussions on this, but I can’t make anything work. Any advice appreciated.

…

Oh, and if anyone knows how I might be able to to tweak the ‘Nothing Found’ message brought up here — your thoughts would be much appreciated. I’ve drawn a blank there, too.

Best, Sarah