Fatal error: Call to undefined function wp()

Hi there, I would very much appreciate your help!

A page on website which I use as a blog is not working, http://jonathanrobson.co.uk/design/

On opening the page you’ll only see:

‘Fatal error: Call to undefined function wp() in /home/e16jona/public_html/design/wp-blog-header.php on line 14’

I must admit, I don’t really know what that means. But I do know how to access the c-panel and look into the file ‘wp-blog-header.php’

This is the file-

<?php
/**
 * Loads the WordPress environment and template.
 * @package WordPress
 */
if ( !isset($wp_did_header) ) {
	$wp_did_header = true;
	require_once( dirname(__FILE__) . '/wp-load.php' );
	wp();
	require_once( ABSPATH . WPINC . '/template-loader.php' );
}
?

As you can see the 14th line does have ‘wp()’ in it, although I don’t know what to do with it.

Iv’e had a look at some possibly similar problems however those who have had them seem to have tried to change code or databases to fix it- I’m not confident in altering things until I can get experts view.

Hope to hear back!

Thanks,

Jonathan